A1 & A8 (Engine Performance, Tune Up and Repair) Vocabulary

I/M Tests

= Inspection and Maintenance tests. Vehicle exhaust gas emissions test required by state governments. The different types are

Efficiency

= Output divided by input a ratio of effective work to the amount of energy expended in producing it

Series-Parallel Circuit

A circuit which is part series and part parallel

Actuator

A control device that delivers mechanical action in response to vacuum or electrical signal. e.g. anything the engine control computer uses to do something such as trigger fuel injection or fire a spark plug.

battery

A device that converts chemical energy to electrical energy

conductor

A material that allows heat and electricity to pass through it.

semiconductor

A material that is neither a good conductor of electricity nor a good insulator, but has properties of electrical conductivity somewhere between the two.

Flux density

A measure of the density of the field lines around a magnet sensor when the tooth of a reluctor aligns with the sensor tip, the magnetic lines of force are squeezed together`, which increases the density

alloy

A mixture of two or more metals e.g. solder = lead + tin

Digital Multi-Meter(DMM)

A piece of test equipment used to measure voltage, current, and resistance in an electronic circuit.

Dial Caliper

A precision measuring device used to measure linear dimensions, thickness, or diameter.

serpentine belt

A ribbed drive belt that drives more than one engine accessory.

connecting rod

A rod that connects the piston and the crankshaft and enables the reciprocating motion of the piston to turn the crankshaft.

watt

A unit of measurement of electrical power, the rate at which electrical energy is dissipated. One volt multiplied by one amp

abrasion

A wearing away or rubbing away by friction.

Combustion

burning of the air/fuel mixture

ignition switch

Key-operated switch mounted in a steering column for connecting and disconnecting power to the ignition and electrical system.

Bimetallic

Made of two kinds of metal with different thermal expansion rates, that when attached to one another, the resulting assembly will bend in the direction of the metal that expands the least

Celcius

Metric temperature scale on which water freezes at 0 degrees and boils at 100 degrees

Camshaft Follower

On OHC engines, this is the equivalent of a rocker arm

BENDIX DRIVE

One type flywheel engaging device for a starting motor. Drive gear that is attached to the starter motor armature and engages the gear teeth on the flywheel.

Backpressure

Pressure created by restriction in an exhaust system.

electric current

The continuous flow of electric charges through a material

Oil clearance

The difference between the inside bearing diameter and the journals diameter. The small space between moving engine parts for the lubricating oil film.

Camshaft Lobe

The eccentric portion of the camshaft that pushes on the valve lifter or camshaft follower and in turn, other valve train components as the camshaft is rotated, to open intake and exhaust valves

Crankcase

The lower part of an engine block that houses the crankshaft.

piston head

The part of the piston that is above the rings

memory

The parts of computer that can store data or instruction, including volatile memory (lost when the computer is turned off) and non-volatile memory (retained when the computer is turned off).

Back pressure

The pressure within a system caused by fluid friction or an induced resistance to flow through the system.

valve spring installed height

the specific distance between the machined spring seat on the cylinder head, to the underside of the valve spring retainer. Both grinding the valve and grinding the valve seat result in an increase in this dimension. A shim can be installed under the spring to restore the original installed height for proper spring tension.

clearance

the specified distance between two components

Camshaft Sprocket

the sprocket on a camshaft that is turned by a chain or belt from the crankshaft. Has twice as many teeth as the one attached to the crankshaft

open loop

the state of an engines control system before it has reached point when the feedback mechanism from the O2 sensor is in operation. The fuel mixture is determined by fixed memory in the computer that correlates specific loads, temperature and speeds with specific quantities of fuel to inject

backfire

the sudden combustion of gasses in the intake or exhaust manifold, resulting in a loud explosion

parting face

the surface of a bearing that contacts the other bearing half when the bearing is assembled

cooling system

the system used to remove excess heat from the engine and transfer it to the atmosphere. Includes radiator, cooling fan, hoses, water pump, thermostat, and engine coolant passages

Blowby

the unburned fuel and products of combustion that leak past the piston rings and into the crankcase at the last part of the combustion stroke

ampere (amp)

the unit for measuring electrical current

lifter

the valve train part that rides on the camshaft lobe

displacement

the volume of a cylinder displaced by the piston as it moves from TDC to BDC (complete stroke)

cylinder walls

the walls of the cylinder bore

lamination

thin layers of soft metal used as the core for a magnetic circuit.

air-fuel ratio

The ratio of air-to-fuel by weight in the fuel mixture drawn into the engine.

ambient temperature

The temperature of the surrounding environment.

power stroke

The third stroke in the four stroke cycle engine when the burning fuel expands and explodes, forcing the piston back down into the cylinder, away from TDC, which then exerts force on the crankshaft.

Ohm

The unit of electric resistance of a circuit in which an electromotive force of one volt maintains a current of one ampere. Symbolized as Ω.

Counterbore

To enlarge a hole to a given depth.

splice

To join or unite together

feeler gauge

thin metal strip manufactured in precise thickness and used to measure clearances.

glaze

thin residue on cylinder walls formed by a combination of heat, engine oil and piston movement.

shim

thin sheets of material, usually metal, used as spacers to control the distance between parts

preload

tightening a bearing a specified amount past zero lash to eliminate axial play

porosity

tiny holes in casting caused by air bubbles

rectify

to change one type of voltage to another

purge

to cleanse or rid of impurities or foreign matter as in carrying off of gasoline fumes from the carbon canister

Countersink

to cut or form a depression to allow the head of a screw to go below the surface.

tap

to cut threads in a hole with a tapered, fluted, threaded tool; a tool used to cut threads in a hole or bore

mesh

to fit closely together or interlock as the fit of gear teeth

grind

to machine a surface with an abrasive wheel

expansion

to make greater in size, in mechanical terms, the expanding in volume of gas in a cylinder of an integral combustion engine after explosion

calibrate

to set, standardize or adjust to achieve accuracy

forge

to shape metal; to stamp into a desired shape

dampen

to slow or reduce oscillations or movement

chase

to straighten or repair damaged threads

deck

top of the engine block where the cylinder head is mounted

foot pound

torque measurement; the energy required to lift one pound one foot high

impedance

total resistance of an electrical device, measured in ohms

ignition coil

transforms the low 12-volt battery ignition primary current into the high voltage secondary current that fires the spark in the plugs The current through the primary coil windings builds up an electromagnetic field around the ferrous core of the coil. When the current is suddenly shut off, the electromagnetic field collapses and generates the high voltage in the secondary windings

torque

twisting effort on a shaft or bolt

Light Emitting Diode (LED)

type of digital electronic display used as either a single indicator or grouped together in a lighting system to show a set of letters or numbers

Actuator activation on computer controlled engine system

typically, activated by grounding their circuits rather than by actively powering them this protects the computer from short circuits

amp (ampere)

unit for measuring the strength (rate of flow) of an electrical current

ohm

unit of electrical resistance

volt

unit of electromotive force. One of these applied steadily to a conductor of one Ohm resistance proceeds a current of one ampere

Crank Web

unmachined portion of the crankshaft that lies between two crank pins or between a crankpin and main bearing journal

degree

used to designate temperature readings or 1 degree as a 1/360 part of a circle

Fuel pressure regulator

uses intake manifold vacuum, or more properly, intake manifold absolute pressure (MAP), to modify the pressure in the fuel rail. Purpose? The fuel pump can pump more fuel than the engine can use, so the system routes the extra fuel back to the tank through this component

compression rings

usually the top two rings on a piston, they form a seal between the piston and cylinder wall to compress the air/fuel mixture in the cylinder

umbrella type valve seals

valve guide seals that fit tightly on the valve stem. They move up and down with the valve stem acting like an umbrella to shield oil away

insert guides

valve guides that are a press fit in the cylinder head

integral guides

valve guides that are part of the cylinder head

ports

valve openings in a cylinder head

integral seats

valve seats that are part of the cylinder head

NOx (oxides of nitrogen)

various compounds of oxygen and nitrogen that are formed in the cylinders during combustion, and are part of the exhaust gas

square wave

voltage fluctuation in an electric circuit that goes immediately from one voltage to the other. These waves are easier for computers to work with, so many vehicles have electronic devices that modify waves into this type. Hall-effect sensors, photoelectric switches and other on-off signal generators produce these types

engine displacement

calculated by multiplying the number of cylinders in the engine with the bore diameter and the length of the stroke

flywheel

cast iron or steel wheel mounted to the end of the crankshaft that helps smooth the engine's power delivery, the teeth around its circumference provides an engagement for the starter. Also provides the mounting points for the pressure plate and friction surface for the clutch

race

channel in the inner or outer ring of an anti-friction bearing in which the balls or rollers operate

Evaporative emission (EVAP) canister

charcoal filled container with lines to the top of the fuel tank, to the intake manifold and to the air cleaner. The charcoal element absorbs fuel vapors from the gas tank and stores them until the engine is operating at normal operating temperatures and speeds. Then, a valve between the canister and engine opens, fresh air is drawn in through the canister air filter and the air and fuel vapors are drawn into the engine and burned, purging the canister

Electrolysis

chemical and electrical decomposition process that can damage metals such as brass, copper and aluminum in the cooling system The decomposition of an electrolyte by the action of an electric current passing through it

Hg

chemical symbol for mercury. Engine vacuum is measured in inches of this

stoichiometric

chemically correct. An air/fuel mixture is considered stoichiometric when it is neither too rich nor too lean; an ideal mixture is composed of 14.7 parts air to 1 part fuel.

series circuit

circuit that has only one path for electric current to follow

abrasive cleaning

cleaning that requires physical abrasion (e.g. glass bead blasting, wire brushing)

Carbon Dioxide (CO2)

colorless, odorless, noncombustible gas, heavier than air, Can be compressed into a super-cold solid known as dry ice. Changes from solid to vapor at -78.5 degrees Celsius

Exhaust gas recirculation valve

component in the EGR system used to meter a controlled amount of exhaust gas into the intake air stream

PCV valve

component that meters crankcase vapors into the intake manifold.

Dieseling

condition by which hot spots in the combustion chamber(s) cause the engine to run after the key is turned off.

slip

condition caused when a driving part rotates faster than a driven part

Ferrous

containing or derived from iron

Evaporative emission (EVAP) canister purge solenoid

controlled by the engine control computer, which determines when the EVAP canister should be purged based on various sensor inputs. When purging is needed, this component controls the vacuum to purge the canister. Generally, it is activated when the engine is running above idle speed and at normal operating temperature

idel air control valve (IAC)

controls the amount of air allowed to bypass the closed throttle to keep the engine at the proper idle speed. It controls airflow through a throttle bypass passageway means of a stepper motor, an electric motor that can move to a specific location in its travel. The computer sends a duty cycle signal to this component to open or close the bypass to increase or slow the idle speed. The signal can range from zero to 100 % and corresponds to the amount of air flow the computer determines is needed. Displayed on the scan tool as counts or %.

anaerobic

curing in the absence of oxygen

aerobic

curing when exposed to oxygen

chafing

damage caused by friction and rubbing.

dwell time

degree of crankshaft rotation during which the primary circuit is on.

runout

degree of wobble outside normal plane of rotation

fatigue

deterioration of a bearing metal under excessive intermittent loads or prolonged operation; in mechanical terms, the tendency of a material, especially metal, to fail under repeated application of stress

fan clutch

device attached to a mechanically driven cooling fan that allows the fan to freewheel when the engine is cold or when the vehicle is driven at speed.

rectifier

device that changes alternating current to direct current

Potentiometer

device that changes voltage by varying its internal resistance.

injector

device that receives metered fuel under relatively low pressure and is activated either electronically or mechanically to spray the fuel under relatively high pressure into the engine.

air pump / thermactor air supply pump

device to produce a flow of air at higher that atmospheric pressure.

water pump

device used to circulate coolant through the engine.

voltage regulator

device used to control the voltage output of an alternator or generator.

throw

distance from center of the crankshaft main bearing journal to center of the connecting rod journal

Crank Throw

distance from the crankshaft main bearing centerline to the connecting rod journal centerline.

installed stem height

distance from the valve spring seat to the stem tip

installed spring height

distance from the valve spring seat to the underside of the retainer when it is assembled with keepers and held in place

arcing

electrical energy jumping across a gap

engine control module (ECM)

electronic computer that controls engine operation. Synonymous with ECA, ECU, SBEC or SMEC. Less powerful than a PCM or VCM as it only pertains to the engine

Pulse Width Modulation (PWM)

electronic control of a solenoid that rapidly cycles it on and off many times per second in order to achieve a specific output

sine wave

voltage fluctuation in an electric circuit that gradually changes, going through the intervening values These types of waves are produced by electromagnetic pulse generators like wheel speed sensors or reluctor type distributer pickup

Ohm's Law

voltage in a circuit is equal to the current multiplied by the resistance

voltage drop

voltage lost by the passage of electrical current through resistance

digital

voltage signal that uses on and off pulses

reference voltage

voltage supplied by the system computer to certain sensors. The sensors reduce the voltage by a specific amount, according to their function, and send the signal back to the computer. The computer then uses the reduced voltage signal to interpret information sent

balance shaft

weighted shaft used on some engines to reduce vibration

counterweight

weights that are part of a crankshaft casting or forging. They counterbalance the weight of the connecting rods and journals to reduce vibration

press fit

when a part is slightly larger than a hole and must be forced together with a press

seize

when a part sticks, preventing the engine from turning e.g. piston welds itself to a cylinder wall because of insufficient clearance or lubrication

undersize

when an inside or outside diameter has been machined to a dimension smaller than standard.

Hall effect

when current flows through a thin wafer of semiconductor material, and a magnetic field crosses it at a right angle, a voltage known as ____ ______ will be generated at the edge of the material. Interrupting the magnetic field turns off the voltage.

piston collapse

when the diameter of the piston skirt becomes less due to heat

siamese ports

when two cylinders are fed through one port

siamese cylinders

when two cylinders are joined at one side without a coolant jacket between them

concentric

when two or more objects share the same center point

valve float

when valve remain open, usually at high rpm, due to weak or broken valve springs

fuel shutoff

works by de-energizing the fuel pump relay. This occurs if the engine speed sensor indicates excessive engine speed or if the vehicle speed sensor indicates a certain mph

Lash Adjuster

a device for adjusting valve lash or maintaining zero lash in certain types of OHC engines. It is stationary in the cylinder head, with one end of a cam follower mounted on top of it. The other end of the follower acts on the valve stem when the cam shaft lobe, which is positioned over the center of the follower, pushes the follower down

thermostat

a device installed in the cooling system that allows the engine to come to operating temperature quickly and then maintain a minimum operating temperature

damper (harmonic balancer)

a device mounted on the front of the crankshaft. It reduces the torsional or twisting vibration that occurs along the length of the crankshaft in multiple cylinder engines.

carburetor

a device that atomizes air and fuel in a proportion that is burnable in the engine

transducer

a device that changes a force into an electrical signal

valve

a device that controls the pressure, direction or rate of flow of a liquid or gas

generator

a device that converts mechanical energy into electrical energy; SAE J1930 nomenclature for an alternator; generating device that uses diode rectifiers to convert AC to DC

engine

a device that converts thermal energy into mechanical energy

Battery

a device that produces electricity through electrochemical action

radiator cap

a device that seals the radiator and maintains a set pressure in the cooling system

choke

a device use on carbureted vehicles to reduce the amount of air entering the intake manifold while leaving the amount of fuel unchanged. Purpose is to richen the mixture enough that a cold engine can still get enough vaporized fuel to start

circuit breaker

a device used in an electrical circuit to interrupt current flow in the event of an overloaded or short

Ohmeter

a device used to measure electrical resistance

Ammeter

a device used to measure strength of electric current flow in a circuit in terms of ampers

switch

a device used to open, close or direct the current in an electrical circuit

oil cooler

a device used to remove heat from the engine or transmission oil. Some use air and others are incorporated into the vehicle's cooling system

Inertia Switch

a device used to shut off a system when disturbed, such as by jarring, tipping, or inversion a switch that automatically shuts off the fuel pump if the vehicle rolls over or is involved in a collision

tensioner

a device used with a timing chain or belt to maintain its tension

Capacitor

a device, made up of two or more conducting plates, separated by an insulator, used to store an electric surge or charge of current

servo, servomotor

a device, such as an electric motor or hydraulic piston, which is controlled by an amplified signal from a low power command device

Direct ignition

a distributor less ignition system in which spark distribution is controlled by the vehicle's computer

vacuum advance

a distributor mounted mechanism that controls spark advance in response to engine vacuum

trip

a driving cycle in an OBD II vehicle that allows a diagnostic test (monitor) to run

dykem blue

a dye that is painted on a valve seat in order to determine seat concentricity. The valve is inserted into the guide, lightly seated, and rotated ~1/8" (3.175mm). A continuous blue line should appear all the way around the valve face if the valve and seat are mating properly. Open patches or breaks in the line indicate that the seat is not concentric and the low spots are not making contact.

ratio

a fixed relation in degrees, numbers, etc. of two similar things

crankshaft thrust collar

a flat machined area that is 90 degrees to the crankshaft main journals. The flange of the thrust main bearing rides against it to control crankshaft end thrust

mushroomed valve stem tip

a folding over of the metal at the tip of the valve stem in response to pounding from too loose a valve adjustment or a defective hydraulic lifter

multi port fuel injection (MFI)

a fuel injection system in which there is one fuel injector for each cylinder.

speed density system

a fuel injection system that calculates the amount of air entering the engine by using the MAP sensor signal, air temp, throttle position sensor signal and volumetric efficiency table (stored in PCM/ECM memory). This system uses no direct measurement of air mass entering the engine as a MAF sensor would

sequential fuel injection

a fuel injection system that uses one electronically pulsed fuel injector for each cylinder. The injectors are pulsed in firing order sequence, ordinarily during the engines intake stroke for that cylinder

port fuel injection (PFI)

a fuel injection system that uses one injector at each cylinder, making fuel distribution exactly equal among all the cylinders

Check Valve

a gate or valve that allows passage of gas or fluid in one direction only.

taper

a gradual decrease in width or thickness; the difference in diameter between the cylinder bore at the bottom of the hole and the bore at the top of the hole, just below the ridge

oil groove

a groove machined in the bearing surface that provides a channel for oil flow.

Carbon

a hard, or soft nonmetallic element that forms in an engine combustion chamber when oil is burned

rigid hone

a hone that removes metal and imparts a precise finish and crosshatch to the bore

flexible hone

a hone used primarily to deglaze cylinder walls aka "ball hone"

missing

a lack of power in one or more cylinders.

miss

a lack of power observed in one or more cylinders either regularly or intermittent

Armature

a laminated, soft iron core wrapped by wire that converts electrical energy to mechanical energy

Aluminum

a lightweight metal used often for cylinder heads and other parts

oil gallery

a line that supplies oil to areas of the engine block or cylinder head

straightedge

a long flat steel strip with perfectly straight edges used for checking surfaces for warpage

Crankshaft

a lower engine part with main and rod bearing journals. Converts reciprocating motion into rotary motion

Align Boring

a machining method that realigns bearing bores to center and makes the bores round

Camshaft Position Sensor

a magnetic reluctance or Hall effect sensor, usually mounted internally in the engine to inform the ECM or PCM of piston position on the intake stroke for timing and synchronization of sequential fuel injection

Crankshaft Position Sensor (CKP)

a magnetic reluctance sensor or "Hall effect" sensor, usually mounted internally in the engine, externally to the engine or in the distributor to inform the ECM or PCM of: -Crankshaft position -location of No. 1 piston -crankshaft speed for ignition timing And other calculations needed by the system where rpm is an input

Variable reluctance sensor

a magnetic sensor that generates its own alternating current voltage based on interference of a moving object across its tip

fuel rail

a manifold used to connect fuel injectors to the fuel pump

antifreeze

a material such as ethylene glycol which is added to water to lower its freezing point, used in an automobile's cooling system

Electrolyte

a material whose atoms become ionized (electrically charged) in solution. In automotive, refers to the mixture of sulfuric acid and water in the battery.

gasket

a material, such as artificial rubber, cork or steel used to seal between parts that would otherwise leak fuel, coolant, lubricants or combustion gasses.

sleeving

a means of reconditioning an engine by boring the cylinder oversize and installing a thin metal liner

go-no-go gauge

a measuring tool that tells whether a tolerance is met or not

fuel pump

a mechanical or electronic device that draws fuel from the fuel tank and sends it to the carburetor or fuel injection system

sending unit

a mechanical, electrical, hydraulic or electro-mechanical device that transmits information to a gauge or other receiving unit

comparator gauge

a metal card with sample patches of various textures to visually compare with a milled or ground surface

fuse

a metal circuit protection device that melts when there is a circuit overload or short

valve guide knurling

a method of refinishing the inside of a valve guide by restoring its original size

disable

a microcomputer decision that results in an automotive system being deactivated.

analog computer

a microprocessor that uses similar electrical signals to make its calculations

compound

a mixture of two or more ingredients

fuel, ignition or spark map

a multidimensional 'map' that correlates engine speed, temperature, load and other factors into a specific spark advance and fuel injection pulse width for that set of conditions. There are several such maps in the computer's hardwired memory. The fine-tuning of the fuel mixture is completed by the signal from the oxygen sensor. On some vehicles, the knock sensor is included to fine-tune the ignition advance to accommodate differences in fuel octane rating and engine wear.

piston slap

a noise that results from excessive piston to cylinder wall clearance

Insulator

a non-conductive material used to insulate wires in an electrical circuit

valve rotator

a part found at the end of some valve springs that rotates the valve each time it opens. This aids in providing even cooling on the valve

intake manifold

a part with runners that connect the fuel system to the intake valve ports

Substrate

a part, substance, or element that lies beneath and supports another part, substance, or element; the reactant in reactions catalyzed by enzymes a ceramic honeycomb grid structure that is coated with catalyst material

seal

a part, usually made of rubber or plastic, installed around a moving part or shaft to prevent leaks

thermal cleaning

a parts cleaning method that uses high temperature in a bake oven to turn grease oil and sludge into a powdery residue, which is then removed by washing, airless shot blasting or glass beading

prussian blue

a paste used to determine the contact area between two parts, such as the height of the valve seat on the valve face

circuit

a path through which electric current can flow before returning to its source

tolerance

a permissible variation between the two extremes of a specific dimension

Floating Pin

a piston pin that moves in the piston and the small end of a connecting rod. Held in place by retaining clips in the pin bosses

rocker arm

a pivot lever mounted on a round shaft or a stud. One end of the rocker rm is applied by the pushrod and the other end acts upon the valve stem

Plastigage

a plastic material that is compressed between a bearing and journal, and the resulting compressed material is measured to determine clearance

thrust plate

a plate behind the cam sprocket that controls camshaft end thrust

throttle position sensor

a potentiometer that is mechanically connected to the throttle shaft the throttle body assembly. It provides an input to the vehicle computer control system regarding throttle position. Reduces the 5 volt reference voltage supplied by the computer to an amount corresponding to the degree to which the driver is holding the throttle open

orifice

a precisely sized hole that controls the flow of fluid

jet

a precisely sized, calibrated hole in a hollow passage through which fuel or air can pass

dial indicator

a precision instrument that is useful in measuring movement of various parts, most often end motion or irregularities

bore gauge

a precision measuring instrument used to measure the diameter of a bore

micrometer

a precision measuring instrument. Measures in thousandths of an inch, one turn of the thimble results in 0.025-in movement of the spindle. 40 threads per inch, therefore 1/40th inch 0.025-in

magnetic particle detection

a process, often called magna flux, which is used with iron or steel parts to detect cracks

tang

a projecting point or prong designed to fit into a handle or shaft; another name for the main or rod bearing shell location lug

flange

a projecting rim or collar on an object for keeping it in place

Force

a pushing effort measured in pounds; the form of energy that puts an object rest into motion or changes the motion of moving object

Crossflow Radiator

a radiator in which coolant enters on one side, travels through tubes and collects on the other side

Downflow Radiator

a radiator in which coolant enters the top and is drawn downward by gravity

ridge

a raised area at the top of a cylinder bore created by ring wear. Occurs because the piston ring does not travel all the way to the top of the bore, thereby leaving an unused portion of cylinder bore above the limit of ring travel. This will usually be more prominent on high milage engines

cylinder sleeve

a replacement iron liner that fits into the cylinder bore. It can be either wet or dry. The outside diameter of the wet style contacts the coolant

pushrod

a rod between the lifter and rocker arm. They are sometimes hollow to allow oil distribution to the valves

eccentric

a rotating part of a shaft that is set off center of the axis the part of the camshaft that operates the mechanical fuel pump

cylinder

a round hole in the engine block for the piston

rocker shaft

a round pipe that is mounted parallel on top of the cylinder head. All of the rocker arms on the head are mounted on it (letter D in picture)

score

a scratch, ridge or groove marring a finished surface

filter

a screen or element that can be made for specified sizes of particles in air or liquid

valve seal

a seal located over the valve stem, used to prevent oil from leaking down the valve guide and into the combustion chamber (letter D)

rear main oil seal

a seal that fits around the rear of the crankshaft to prevent oil leaks

O-ring seal

a sealing ring, usually made of rubber and installed in a groove; a type of valve seal that fits into a valve stem groove under the valve keepers

mass air flow (MAF) sensor

a sensor in a fuel injection system that measures the mass (weight/density) of he incoming air flowing through a meter. The measurement transmitted to the PCM is usually either a frequency or a voltage

Mass air flow (MAF) sensor

a sensor in a fuel injection system that measures the mass (weight/density) of the incoming air flowing through a meter. The measurement transmitted to the PCM/ECM is usually either a frequency or a voltage

closed loop

electronic feedback system in which sensors provide constant information on what is taking place in the engine; the state of the engine control computer system when it is working normally, at full operating temperature and normal speeds with the oxygen sensor switching. The fuel injection quantity is determined by the set of inputs from the engine control computer's sensors, most specifically the O2 sensor in the exhaust stream. The system samples its output and uses that sampling to modify the next inputs.

electrode (anodes and cathodes)

a terminal that conducts an electric current into (anode) or away (cathode) from the conducting part of a circuit, such as the terminals of a battery; firing terminals found in a spark plug

combustion chamber

enclosure formed in the cylinder head at the top of the piston, where the spark plug ignites the compressed air-fuel mixture. = the volume of the cylinder above the piston when the piston is at TDC

fan shroud

enclosure that routs air through the radiator cooling fins.

cylinder balance test (power contribution test)

engine diagnostic test used to compare the power output of all cylinders.

spark knock

engine noise caused by abnormal uncontrolled combustion due to preignition or detonation

splines

external or internal teeth cut into a shaft; used to keep a pulley or hub secured on a rotating shaft.

misfire

failure of an explosion to occur in one or more cylinders while the engine is running; can be continuous or intermittent failure

misfiring

failure of an explosion to occur in one or more cylinders while the engine is running; can be continuous or intermittent failure.

electrode

firing terminals found in a spark plug

Diaphragm

flexible, impermeable membrane on which pressure acts to produce mechanical movement In automotive, they can range from thin membranes that separate two chambers to large metal discs that activate clutch plates

discharge

flow of current from a battery; to remove the refrigerant from an A/C system

Fuel Trims (General)

fuel delivery (volume) adjustments based on closed loop feedback. Values above the nominal value (0%) indicate increased injector pulse width (IPW) or a richening air/fuel ratio; values below 0% indicate decreased IPW or a leaning air/fuel ratio.

direct injection

fuel injection system wherein fuel is sprayed directly into the combustion chamber. Therefore, there are no precombustion chambers or or manifold injection

Short Term Fuel Trim (STFT)

fuel trim value based on current O2 sensor switching values

Long Term Fuel Trim (LTFT)

fuel trim value that is learned and used to compensate for continual deviation of STFT from nominal value

timing gears

gears that drive the camshaft from the crankshaft

AIR system upstream air injection

goes into the exhaust manifold to assist in after-burning Hydrocarbon laden exhaust gasses

AIR system downstream air injection

goes into the oxidation bed of the catalytic converter to help oxidize hydrocarbon and carbon monoxide (CO) emissions

corrode

gradual loss

Carbon (C)

hard or soft nonmetallic element that forms in and engines combustion chamber when oil is burned

axial

having the same direction or being parallel to the axis of rotation

torque-to-yield head bolts

head bolts that are often not reusable. They have been purposely stretched beyond the point where they will return to their original length. This provides more uniform clamping force

exhaust-gas-recirculation system (EGR)

helps prevent the formation of oxides of nitrogen (NOx) by recirculating a certain amount of exhaust as an inert gas through the intake manifold to keep the peak combustion temperatures below what would form those chemical compounds. The computer determines when and how much exhaust to recirculate based on information from all its other sensors. It then actuates the solenoid which opens a vacuum circuit or operates an electronic circuit to actually work the EGR valve. The computer uses a "duty-cycle" (% on-time) signal to activate the solenoid

secondary circuit

high-voltage side of the ignition system, usually above 20K volts. Includes ignition coil, spark plug wires and spark plugs.

wrist pin

hollow metal tube that secures the piston to the connecting rod and allows the piston to swivel on the rod. Also called a piston pin.

gassing

hydrogen bubbles that rise from the battery electrolyte during charging

Compression

in a solid material, compression is the opposite of tension. In a gas, compression causes the gas to be confined in a smaller area, raising its temp and pressure

compression

in a solid material, this is the opposite of tension. In a gas, it causes the gas to be confined in a smaller area, raising its temperature and pressure

emitter

in a transistor, the region or layer of semiconductor material from which electrons are injected into the base region

period

in an electrical signal, this is the amount of time it takes for one cycle of an electrical signal to repeat itself; the number of these that occur in one second is the frequency of the signal

reluctor

in an electronic ignition, the trigger wheel mounted on the distributor shaft that triggers the pickup coil, which in turn signals the control module to fire the coil

core

in automotive terminology, the main part of a heat exchanger, such as a radiator, evaporator or heater. Usually made of tubes, surrounded by cooling fins, used to transfer heat from the coolant to the air

analog

in automotive, a device, such as a gauge, that uses a needle and printed reference, rather than an electronic readout

acidity

in lubrication, the presence of acid type chemicals which are identified by the acid number. Within oil, it causes corrosion, sludges and varnish to increase

Excessive wear

in mechanical terms, wear of a component that exceeds designed limits; wear caused by overloading a part that is in an out-of-balance condition, resulting in an lower-than-normal life-expectancy of the part being subjected to the adverse operating condition

load

in mechanics, the amount of work performed by an engine; specifically, the external resistance applied to the engine by the machine it is operating. In electrical terms, the amount of power delivered by a generator, motor, etc., or carried by a circuit. The work an engine must do, under which it operates more slowly and less efficiently (e.g., driving up a hill, pulling extra weight).

ammeter

instrument used to measure electrical current flow in a circuit

Roller lifter

lifters that are equipped with rollers at the bottom that ride on the camshaft lobe, in order to reduce friction

roller lifter

lifters that are equipped with rollers at the bottom that ride on the camshaft lobes in order to reduce friction

mushroom lifters

lifters with contact faces that are wider than the lifter bore. They must be installed through the bottom of the lifter bores, before the cam is installed

radial load

load applied at 90 degrees to an axis of rotation.

thrust load

load placed on a part that is parallel to the center of the axis.

I/M 240

loaded mode transient test that measures hydrocarbons, CO, CO2, NOx and O2 second by second. The gas parameters are in grams per mile (rpm_. The vehicle is driven on a dynamometer at various speeds and loads, accelerating and decelerating for 240 seconds. This test is taken in part from the Federal Test Procedure (FTP) required of OEMs for federal emissions certification

primary circuit

low-voltage circuit of an ignition system

Bearing Race

machined circular surface of a bearing against which the roller or ball bearings ride

crankpin

machined, offset area of a crankshaft where the connecting rod journals are machined

mill

machining with rotating tooth cutters

integral

made of one piece

additive

material added to the engine oil to give it certain properties

No-load I/M tests

measure HC emissions in PPM and CO emissions in % while the vehicle is in neutral with the engine running at idled/or 2500 rpm. Sometimes CO2 is measured in % as a verification gas

manifold absolute pressure

measure of the degree of vacuum or pressure within an intake manifold.

bolt diameter

measurement across the major diameter of a bolts threaded area or the bolt shank

heat range

measurement of a spark plug's ability to dissipate heat from its firing end.

horsepower (hp)

measurement of an engines ability to perform work = the energy required to lift 550 lbs. 1 foot in 1 second

Acceleration simulation mode (ASM) - loaded mode I/M tests

measures HC, CO, and NOx emissions while the vehicle is driven on a dynamometer at a fixed speed and load Includes ASM 5015: is done at 15 mph with a load of 50% of the power needed to accelerate the vehicle from 15mph 65 mph in 15 seconds. ASM 2525 is a test at 25 mph with a load of 25% of the same power

fan

mechanically or electrically driven propeller that draws or pushes air through the radiator. condenser, heater core or evaporator core

cooling fan

mechanically or electrically driven propellor that draws air through the radiator

valve spring seats

metal shims used, usually on aluminum cylinder heads, to protect the head from the bottom of the valve spring

ferrous metal

metal that contains iron or steel and is subject to rust.

casting

metal that is manufactured by pouring it into a mold. It is more porous than forged metal and does not conduct heat as well. Less expensive to manufacture

coolant

mixture of water and ethylene glycol-based antifreeze that circulates through the engine to help maintain proper temperatures.

play

movement between two parts

axial play

movement parallel to the axis of rotation

camshaft follower

on OHC engines, the equivalent of a rocker arm

valve margin

on a poppet valve, the space or rim between the surface of the head and the surface of the valve face

Power Train Control Module (PCM)

on vehicles with computer control systems, the main computer that determines engine operation based on sensor inputs and actuator outputs. May also control transmission

Powertrain Control Module (PCM)

on vehicles with computer controlled systems, the main computer that determines engine operation based on sensor inputs and actuator outputs. May also control transmission operation

Heli-coil

one type of thread repair device that consists of a spring loaded stainless steel coil

Freeze-Frame Data

parameters / values of engine and powertrain operation that are stored the instant a diagnostic trouble code (DTC) is set and entered into diagnostic memory. (OBD II systems)

heat sink

part of a system designed to be at a lower temperature than its surroundings, used to dissipate heat from that system. Dissipates heat and protects parts

Negative Temperature Coefficient (NTC) Thermistor

a thermistor that loses electrical resistance as it gets warmer. The type of temperature sensors used for computer control system. The effect is to systematically lower the 5-volt reference voltage sent to them by the computer, yielding a signal that corresponds to the temperature of the measured source. Examples: ECT and IAT

valve guide liner

a thin bronze bushing installed in a valve guide to restore it to original size

liner

a thin layer used as a wear surface or a replaceable guide liner or cylinder sleeve

sleeve

a thin metal liner, such as is commonly used in a cylinder bore

thread chaser

a tool for cleaning threads that will not remove any metal

multimeter

a tool that combines the functions of a voltmeter and ammeter into one diagnostic instrument

Multimeter

a tool that combines the functions of a voltmeter, ohmmeter and ammeter into one diagnostic instrument

valve spring compressor

a tool used to compress the valve spring on a cylinder head. Necessary in order to remove the keepers.

voltmeter

a tool used to measure voltage available at any point in an electrical system

ridge reamer

a tool used to remove the ridge from the top of a cylinder bore

ring file

a tool used to trim the ends of a piston ring to bring the ring end gap within specification

timing belt

a toothed reinforced belt used to drive the camshaft from a sprocket on the crankshaft

gear

a toothed wheel, disc, etc. designed to mesh with another or with the thread of a worm; used to transfer or change motion

split-ball gauge

a transfer measuring instrument. Turning the handle on the gauge causes the split ball to expand. It can be used for measuring small holes such as valve guides

air duct

a tube, channel or other tubular structure used to carry air to a specific location

plain bearing

a type of bearing where the load is supported on a thin film of pressurized oil

liquid crystal display (LCD)

a type of digital electronic display made of special glass and liquid; requires a separate light source

axial load

a type of load placed on a bearing that is parallel to the axis of the rotating shaft

Random Access Memory (RAM)

a type of memory used in a computer to store information temporarily

distributor

part of an ignition system that triggers the spark and directs it through wires and into spark plugs

bolt head

part of the bolt that the socket or wrench fits over in order to torque or tighten the bolt

exhaust manifold

part of the exhaust system that is connected to the cylinder head.

bearing

part that supports and reduces friction between a stationary and moving part or two moving parts

valvetrain

parts that convert camshaft movement to valve movement. Includes camshaft, cam timing part, lifters or cam followers, pushrods, rocker arms, valves and springs

Valvetrain

parts that convert camshaft movement to valve movement. These include the cam, cam timing parts, lifters, cam followers, pushrods, rocker arms, valves and springs

harmonic vibration

periodic motion or vibration along a straight line. The severity depends upon the frequency or amplitude

read-only memory (ROM)

a type of memory used in microcomputers to store information permanently, as opposed to the temporary storage provided by RAM

positive seal

a type of valve seal that fits tightly around the top of the valve guide

poppet valve

a valve consisting of a round head with a tapered face, an elongated stem that guides the valve and a machined slot at the top of the stem for a valve spring retainer

vehicle speed sensor (VSS)

permanent magnet sensor that provides input to the vehicle computer control system regarding vehicle speed.

transverse

perpendicular or at a right angle to a front-to-back centerline

radial

perpendicular to the shaft or bearing bore

electronic

pertaining to the control of systems or devices by the use of small electrical signals and various semiconductor devices and circuits

dowel

pin extending from one part to fit into a hole in an attached part; used for location and retention.

exhaust pipe

pipe between the exhaust manifold and muffler.

core plugs

plugs that fill holes in a block or head left from the casting process. AKA freeze, welsh or expansion plugs

saturation

point at which current flowing through a coil or wire has built up the maximum magnetic field

exhaust valves

poppet valves in the cylinder head that control the flow of exhaust from the engine.

gear pump

positive displacement pump that uses two meshing external gears, one drive and one driven.

harmonics

potentially damaging vibrations in the crankshaft or valve springs

vacuum

pressure lower than atmospheric

Alternating Current (AC)

rapid and interrupted current, flowing first in one direction and then in the opposite direction

Octane (C8H18)

rating indicating a fuel's tendency to resist detonation

mechanical efficiency

ratio between the indicated horse-power and brake horse-power of any given engine

Compression Ratio

ratio of the volume in the cylinder above the piston when the piston is at bottom dead center compared to the volume in the cylinder above the piston when the piston is at top dead center

thermal efficiency

ratio of work accomplished compared to total quantity of heat contained in fuel. Fuel contains potential energy in the form of heat when burned in the combustion chamber

contraction

reduction in mass or dimension

ignition timing

refers in crankshaft degrees to the position of the piston in the cylinder when the spark occurs

timing

refers in crankshaft degrees to the position of the piston in the cylinder. When referring to camshafts, it is when the valves open. When referring to ignition, it is when the spark occurs

electromechanical

refers to a device that incorporates both electrical and mechanical principles together in its operation.

out-of-round

refers to an inside or outside diameter that was originally designed to be perfectly round, but instead has varying diameters when measured at different points across its diameter

self-diagnostics

refers to the way in which the computer in the ECM or PCM systems constantly monitors the state of each of its sensors and actuators. If one of them produces an implausible signal, or no signal at all, the system registers a fault code

Manifold vacuum

relatively low pressure in an engine's intake manifold just below the throttle (plate(s). It is highest at idle and drops during acceleration

manifold vacuum

relatively low pressure in an engine's intake manifold just below the throttle plate(s). Highest at idle and drops during acceleration

chemical cleaning

relies primarily on chemical action to remove dirt, grease, scale, paint or rust.

Residual pressure

remaining or leftover pressure.

friction

resistance to motion that occurs when two objects rub against each other

ballast resistor

resistor in the primary side of the ignition system, which is used to reduce voltage by approximately 4-5 volts.

Variable resistor

resistor that can be adjusted so the amount of resistance produced in the circuit changes.

vehicle control module

same as a PCM with aded circuits for some chassis systems such as traction control, cruise control, etc

scuffing

scraping and heavy wear from the action of a piston on cylinder walls.

EGR Valve position sensor

sensor mounted on EGR valve that signals the ECM regarding EGR valve pintle position and EGR flow

piezoelectric sensor

sensor that generates voltage from physical shock or motion, such as a knock sensor.

magnetic pulse generator

sensor used to monitor the position of a rotating part such as a crankshaft or input shaft.

valve timing

set rotations of the camshaft and crankshaft to open/close valves at proper intervals during the piston strokes for optimal operation of an engine

key

small block inserted between the shaft and hub to prevent circumferential movement

keepers

small locks that hold the valve retainer onto the valve stem. Also called "split locks"

valve keepers

small locks that hold the valve retainer onto the valve stem. Also called split locks

Hydrocarbon (HC)

solid particles of gasoline present in the exhaust and in crankcase vapors that have not been fully burned

ID

stands for "inside diameter"

OD

stands for "outside diameter"

battery acid

sulfuric acid solution used as the electrolyte in a battery.

pitting

surface irregularities caused by corrosion.

Evaporative emission (EVAP) canister purge valve

a valve on the line between the EVAP canister and the intake manifold. When the engine is running, under certain operating conditions, this component opens, fresh air is drawn in through the canister air filter, and the air and fuel vapors are drawn into the engine and burned, purging the canister.

Rheostat

a variable resistor used to control current flow in a circuit

reference pulse

a voltage signal generated by the crankshaft position sensor (or distributor or cam position sensor - all equivalent components for this purpose). The voltage signal is sent to the computer as a fixed number of degrees BTDC for each cylinder, with the signal for cylinder 1 distinguishable from the others

pickup coil

a weak, permanent magnet-and-wire assembly which forms a position sensor.

Ethanol

a widely used gasoline additive known for its abilities as an octane enhancer

field coil

a wire coil on an alternator rotor or starter motor frame; produces a magnetic field when energized.

Charging system

system that supplies electrical power for vehicle operation and recharges the battery.

knurling

technique used for restoring the inside diameter dimensions of a worn valve guide by plowing tiny furrows through the surface of the metal

reaming

technique used to repair worn valve guides by increasing the guide hole size to take an oversized valve stem, or by restoring he guide to its original diameter

Farenheit

tempurature scale on which water freezes at 32 degrees and boils at 212 degrees

detonation

abnormal combustion of an air/fuel mixture. When pressure in the cylinder becomes excessive and the mixture explodes violently, instead of burning in a controlled manner. The sound can be heard as the cylinder walls vibrate. ***do not confuse with "preignition" or "ping"***

hone

abrasive tool for correcting small irregularities or differences in diameter in a cylinder, such as an engine cylinder or brake caliper; to enlarge or smooth a bore with a rotating tool containing abrasive material

smog

air pollution that forms when ozone and vehicle exhaust react with sunlight

boost pressure

term used when a turbocharger increases the air pressure entering an engine above atmospheric pressure

intake valve

also called "inlet valve", it closes off the intake ports and opens it at the correct time in response to movement from the cam lobe

water jacket

also called a cooling jacket, it is the hollow area of a casting designed for coolant flow

throttle body injection (TBI)

also called central fuel injection, it has an intake manifold like that used with a carburetor. One or more injectors are mounted in the component which resembles a carburetor in physical appearance

calculated load value

the % of engine capacity being used, calculated by the ECM or PCM based on current air flow divided by known maximum air consumption of the particular engine under test. On a scan tool, show as a ENG LOAD %:

Embedability

the ability of the bearing lining material to absorb dirt.

end-play

the amount of axial or end-to-end movements in a shaft due to clearance in the bearings

lash

the amount of clearance between components in a gear train or valve train

valve lash

the amount of clearance in the valvetrain when the lifter is on the base circle of the camshaft lobe

cold cranking amps (CCA)

the amount of cranking amperes that a battery can deliver in 30 seconds @ 0 degrees Fahrenheit (-18 Celsius)

Amperage

the amount of electrical current flowing in a circuit

bearing clearance

the amount of space left between a shaft and the bearing surface for lubricating oil to enter.

margin

the area between the valve face and the head of the valve

valve face

the area of the valve that contacts the valve seat

land

the areas between the grooves of a piston

magnetic field

the areas surrounding the poles of a magnet that are affected by its forces of attraction or repulsion; the region of space in which there is a measurable magnetic force

normal wear

the average expected wear when operating under normal conditions.

millimeter

the base of metric size measurement. One is equal to 0.039370-in. One inch is equal to 25.4 of these

camshaft journal

the bearing area of a camshaft

crankshaft journals

the bearing areas of a crankshaft; the main and rod journals

bearing crush

the bearing is slightly larger at its parting lines so that when the two halves of the bearing are tightened together, the bearing seats firmly in its bore. This keeps the bearing from rotating

bearing lining

the bearing surface area of a bearing, it is usually made up of an alloy of several metals, including lead

Crankshaft Pulley

the belt drive pulley mounted on the front of the vibration damper

oil rings

the bottom ring on the pistons, scrapes excess oil from the cylinder walls to keep it from entering and burning in the combustion chamber

atomization

the breaking down of a fluid into a fine mist that can be suspended [is lighter than] air

combustion

the burning of the air/fuel mixture

energy

the capacity to do work and overcome resistance

power

the capacity to exert physical force or energy measured in terms of the rate at which it can be exerted, e.g. HP or watts

engine block

the casting made up of cylinders and the crankcase

cylinder head

the casting that contains the valves and valve springs, and covers the top of the cylinders

pintle

the center pin used to control fluid passing through a hole; a small pin or point shaft used to open or close a passageway.

main bearing journal

the central, load-bearing points along the axis of a crankshaft, where the main bearings support the shaft in the block

zirconium

the ceramic material from which the middle section of the oxygen sensor is made, It functions as a solid electrolyte once the O2 sensor is working (as a battery) to send the exhaust sampling signal back to the computer

Corrosivity

the characteristic of a material that enables it to dissolve metals, other materials or burn the skin.

ring end gap

the clearance between the ends of a piston ring when installed in the cylinder bore

main bearing clearance

the clearance between the main bearing journal and its bearings

backlash

the clearance or play between two parts, as in gear mesh

fuel pump relay

the computer controls the electric fuel pump by energizing this component. It does so by grounding this component's circuit, which then directly supplies power to the fuel pump.

power circuit

the part of the circuit that is connected electrically to the positive terminal of the battery. Every electric circuit has a power and a ground side. On computer controlled systems, ordinarily power is routed to actuators directly through the ignition switch; the circuit is completed when the computer grounds it. Most manual switches directly connect the power side of the circuit to the load. Fuses are ordinarily positioned as close as possible to the battery on the power side of a circuit

Frequency

the number of cycles of a periodic waveform, typically measured in one second intervals or hertz (cycles per second)

current

the number of electrons flowing past a given point in a given amount of time

thread pitch

the number of threads in one inch of threaded bolt length. In the metric system, the distance in millimeters between two adjacent threads.

Resistance

the opposition offered by a substance or body to the passage of electric current through it

resistance

the opposition offered by a substance or body to the passage of electric current through it

heel

the outside or larger part of a gear tooth; or, the bottom of the cam lobe's base circle

boss

the part of a piston that fits around its pin

pin boss

the part of a piston that fits around its pin

Battery Cell

the part of a storage battery made from two dissimilar metals and an acid solution. Stores chemical energy to be used later as electrical energy.

high tension

the part of a system that operates under or carries high voltage; in an ignition system, voltages in the secondary circuit of the system as opposed to the low, primary circuit voltage

Base circle

the part of the camshaft lobe that is opposite the tip of the nose. The part that DOES NOT move the valve in any way

Preignition

also called ping, is the abnormal combustion of the air/fuel mixture before it is time to do so. A hot surface of of carbon deposits in the combustion chambers ignites the air/fuel mixture before the spark is fired. The sound can be heard as the cylinder walls vibrate. Not to be confused with detonation.

radiator

the part of the cooling system that acts as a heat exchanger, transferring heat to the atmosphere. It consists of a core and holding tanks connected to the cooling system by hoses

valve stem

the part of the valve that is inside the valve guide

valve spring retainer

the part that connects the valve spring to the valve and holds the valve against the cylinder head. It is held to the valve by keepers.

oil pan

the part that encloses the crankcase at the lower end of the block

polarity

the particular state (positive or negative) with reference to the two magnetic poles

intake port

the passage or opening in a cylinder head that is closed by the intake valve.

exhaust port

the passage or opening in a four stroke cylinder head for the exhaust valve

Crosshatch

the pattern left on a finished cylinder wall; retains oils and aids piston ring seating

Connecting rod bearing

the plain bearing shells located in the big end of the connecting rod that support the connecting rod and piston on the crankshaft

main bearings

the plain bearings that support the crankshaft in the engine block

overlap

the point at TDC where both valves are open at the same time. The intake valve is just beginning to open while the exhaust valve is just finishing closing

Microprocessor

the portion of a microcomputer that receives sensor input and handles calculations

Top Dead Center (TDC)

the position of the crankshaft for a specific cylinder when the piston is at the highest point in its vertical travel

atmospheric pressure

the pressure exerted on an object by the weight of the earths atmosphere = 14.7 psi (101 kPa) at sea level and less as you reach higher altitude

Oil Pressure

the pressure that results from resistance to flow from the oil pump. As the pump turns faster, it produces more flow. A relief valve limits the amount of pressure it can produce

heated oxygen sensor (HO2S)

an O2 sensor with a resistance element built into it to shorten the time needed to bring the sensor to operating temperature. The same resistance element will keep the sensor at operating temperature during idle, low speeds and in very cold weather.

alignment

an adjustment to bring into a line

shunt

an alternate path through which electrical current or fluids may flow

ball bearing

an anti-friction bearing that uses a series of steel balls held between inner and outer bearing races

Roller Bearing

an anti-friction device made up of hardened inner and outer races between which steel rollers move

hydraulic valve lifter

an automatic lash adjusting device that provides a rigid connection between the camshaft and valve, while absorbing the shock of motion. This style differs from the solid type in that it uses oil to absorb the shock that results from movement of the valvetrain

stepper motor

an electric motor that can move to a specific position on its range of travel

elasticity

the principle by which a bolt can be stretched a certain amount. Each time the stretching load is reduced, the bolt returns to exactly its original size

integrated circuit

an electrical circuit containing many interconnected amplifying devices and circuit elements formed on a single body or chip of semiconductor material; diodes, transistors and other electronic components mounted on semiconductor material and able to perform numerous functions

printed circuit

an electrical circuit formed by electrically conductive paths printed on a board

open circuit

an electrical circuit that has a break, an intentional (switch) or unintentional (bad connection) break in the wire, preventing the flow of electrons

resistor

an electrical device installed in a circuit to lower voltage and current flow

spark plug

an electrical device that is connected to a high voltage source. The high voltage travels down an electrode inside this component and arcs across an air gap, thereby creating the spark that starts the combustion process in the combustion chamber

solid state

an electrical device with no moving parts

relay

an electromagnetic switch that uses low amperage current to control a circuit with high amperage

module

an electronic control unit

transistor

an electronic device produced by joining three sections of semiconductor materials, used as a switching or amplifying device

fuel injector

an electronically-opened nozzle that sprays finely atomized fuel through its aperture into the intake manifold during a cylinder's intake stroke. On some vehicles, these injections are sequential, another's the injectors are fired all at once or in banks

catalytic converter

an emission control device located in the exhaust system that contains catalysts, which reduce hydrocarbons, carbon monoxide and nitrogen oxides in the exhaust gases.

Evaporative emission (EVAP) system

an emission control system that prevents hydrocarbon (HC) emissions from escaping the fuel system into the atmosphere

valve cover

an enclosure fastened to the top of a cylinder head, over the valve-train

cylinder power balance test

an engine diagnostic test used to compare the power output of all the engines cylinders AKA power contribution test

ground circuit

the part of the circuit that is connected electrically to the negative terminal of the battery. Resistance in this circuit will reduce the current through it and cause deterioration in the function of the circuit

Induction

the process by which an electric or magnetic effect is produced in an electrical conductor or magnetic body, when it is exposed to variation of a field of force. This is the principle used in an ignition coil to increase voltage

evaporation

the process in which a liquid is turned into vapor

dilution

the process of adding solvent to lower the concentration of solute in a solution "to make thinner, or weaker"

oxidation

the process of combining oxygen, resulting in rusting or burning. Rust is an example of slow, fire is an example of fast

lapping

the process of fitting one surface to another by rubbing them together with an abrasive material between the two surfaces

electromagnetic induction

the process of generating a current by moving an electrical conductor relative to a magnetic field

lubrication

the process of introducing a friction reducing substance between moving parts to reduce wear

aeration

the process of mixing air with liquid

oil pump

the pump that circulates lubricating oil throughout the engine, usually driven by the camshaft (by way of the distributor)

Cylinder Leakage Test

an engine diagnostic test where the piston is brought to TDC on the compression stroke and compressed air is pumped into the cylinder through the spark plug hole. Where the air leaks out is the location of the compression leak. ***A leakage tester will compare the air leaking out of the cylinder to the amount of air being put in, expressed as a percentage***

turbocharger

an exhaust driven pump that compresses intake air and forces it into the combustion chambers at higher than atmospheric pressure. The increased air pressure allows more fuel to be burned and results in increased HP

barometric pressure

the pushing force of the atmosphere, usually expressed in terms of the height of a column of mercury. A sensor or its signal circuit sends a varying frequency signal to the processor relating the actual measurement

ring lands

the raised parts between the piston ring grooves

Density

the ratio of the mass of an object to its volume

specific gravity

the ratio of the weight or mass of the given volume a substance that of an equal volume of another substance, e.g. water for liquids and solids, air or hydrogen for gasses, are used as standards

leakdown

the relative movement of the plunger with respect to the hydraulic lifter body after the check valve is seated by pressurized oil. A small amount of oil leak down is necessary for proper hydraulic valve lifter operation

main bearing caps

the removable lower halves of the main bearing bores

connecting rod cap

the removable part of the big end of the connecting rod

Friction

the resistance that one surface or object encounters when moving over another.

oil pump pickup

the screen that filters and keeps debris out of the oil pump

Compression Stroke

the second stroke of the 4-stroke engine cycle, in which the piston moves from bottom dead center and the intake valve is closed, trapping and compressing the air/fuel mixture in the cylinder

major and minor thrust surfaces

the sides of a piston. The major receives most of the load from crankshaft rotation

skirt

the sides of the piston that are against the cylinder walls

electronic ignition (AKA distributorless ignition, direct ignition, coil-near-plug ignition or coil-over-plug ignition)

an ignition system that does not use a distributor but instead has coils dedicated to individual spark plugs or pairs of spark plugs. A system in which the timing and firing of the spark plugs in controlled by an ECU

meter

an instrument used for measuring, especially the flow of a gas, liquid or electrical charge, to regulate the flow of gas, liquid or electrical charge, to control the amount of fuel passing into an injector or carburetor

profilometer

an instrument used to measure surface profiles and surface roughness

electromagnet

an iron core surrounded by a coil of wire that temporarily becomes a magnet when an electric current flows through the wire.

adhesion

an oils ability to cling to a surface

piston ring

an open-ended ring that fits into a groove on the outer diameter of the piston. Its chief function is to form a seal between the piston and the cylinder wall. Most automobiles have three, 2 for compression and one for oil

glass bead blasting

an operator intensive abrasive cleaning method that uses glass beads propelled by compressed air in an enclosed blasting cabinet

magnet

any material that attracts iron and materials that contain iron

sensor

any mechanism by which the ECM can measure some variable on the engine, such as coolant temp or engine speed. Each one works by sending the computer a signal of some sort.

flutter

as applied to engine valves, refers to a condition wherein the valve is not held tightly on its seat due to a weak valve spring, during the time the cam is not lifting it

dropping resistor

battery voltage reduction device.

deflection

bending or movement away from the normal position due to loading.

Air injection reaction (AIR) system air sources

-Via pulse-air pump or an electronically or belt driven pump

pinning

a crack repair method, also called stitching or pegging

bore

a cylindrical hole

cylinder bore

a cylindrical hole

amplify

(v.) to make stronger, larger, greater, louder, or the like

OHC engine (overhead cam)

An engine with the camshaft located in the cylinder head

Four-stroke cycle engine

An engine, either gas or diesel that uses 4 strokes: intake, compression, power and exhaust. A firing impulse occurs every two turns of the crankshaft. AKA "Otto cycle" engine after the name of the gasoline version inventor and "Diesel Cycle" engine named after Rudolf Diesel

hydrometer

An instrument for determining the density of solids and liquids by flotation (specific gravity)

Oscilloscope

An instrument that displays an electrical signal as a voltage against time trace on a screen

Carbon Monoxide (CO)

Colorless, odorless, poisonous gas produced by incomplete combustion. It is absorbed by the bloodstream 400 times faster than oxygen

ignition system

Components that produce a spark to ignite the air-fuel mixture in the combustion chamber.

Farenheit to Celsius

C= 5/9 (F-32)

Direct Current (DC)

Electric current that flows in only one direction

brush

a bar of conductive material that rides on the commutator of a generator or motor

feedback

a basic concept in the way the engine control system works. Refers to the mechanism whereby the computer is able to measure the oxygen in the exhaust stream and then modify the amount of fuel injected into the intake manifold, to optimize exhaust emissions by keeping the air/fuel ratio at stoichiometry

Insert bearing

a bearing made as a self-contained part and then inserted into the bearing housing

journal

a bearing surface on a shaft

Camshaft Bearing

a bearing that supports the camshaft journal. On some engines it is full round and pressed in place. On some OHC engines, it is made up of two shells like a connecting rod bearing

fatigue strength

a bearings ability to withstand loads

Alternator

a belt driven device that provides electrical current for the vehicles charging system converts mechanical energy into electrical energy generating device that uses diode rectifiers to convert AC to DC

Chamfer

a bevel or taper at the edge of a hole or corner, usually cut at 45 degrees

valve guide

a bore in the cylinder head that the valve stem fits into

wastegate

a bypass valve that limits boost produced by a turbocharger

runner

a cat tube on an intake or exhaust manifold used to carry air in or out of the engine

three-way catalytic converter

a catalytic convertor system that reduces exhaust gas emission levels, Usually consists of two beds of catalyst, the upstream (reduction bed) reducing NOx emissions and oxygen and the downstream (oxidation bed) reducing HC and CO emissions to CO2, O2 and H2O.

monolithic substrate

a ceramic honeycomb structure in a catalytic converter that is coated with the catalysts

timing chain

a chain that drives the camshaft from a sprocket on the crankshaft

amplifier

a circuit or device used to increase the voltage or current of a signal

insulated circuit

a circuit that includes all of the high current cables and connections from the battery to the starter motor.

parallel circuit

a circuit with more than one path for an electric current

jet clean

a cleaning machine that sprays engine parts with degreasing solution under high pressure. The parts rotate on a carousel during the cleaning process to expose all surface to the cleaning spray

solenoid

a coil of wire that becomes an electromagnet when current flows through it. It then loses its magnetism when the current flow is turned off. Contains an iron plunger inside the wire coil that is spring loaded to one position. When energized, the plunger moves to the other position

methanol (methyl alcohol) 3H-C-OH

a colorless, flammable, highly volatile liquid obtained by the distillation of wood and synthesized chiefly from carbon monoxide and hydrogen. It is used as a fuel and a solvent. It is the lightest and simplest alcohol.

Hemispherical combustion chamber

a combustion chamber shape that resembles a half a globe the valves are on the sides of the spark plug, which is in the center

rotor (distributor)

a component mounted on the shaft of the distributor that transfers voltage from the distributor cap center terminal (coil wire) to the spark plug wire terminals

intercooler

a component on some turbocharged engines used to cool the compressed intake air

detergent

a compound of soap like nature used in engine oil to remove engine deposits and hold them in suspension in the oil

catalyst

a compound, or substance that can speed up or slow down the reaction of other substances without being consumed itself. e.g. platinum or palladium are used to promote combustion of unburned hydrocarbons and reduce carbon monoxide

supercharger

a compressor, mechanically driven by the engine's crankshaft, which pumps air into the intake manifold

surging

a condition in which the engine speeds up and slows down even when the throttle is held steady.

flooding

a condition in which unvaporized fuel in the intake manifold and/or combustion area prevents the engine from starting

warpage

a condition that exists when a part is bent or twisted; the degree to which the part deviates from flatness

short circuit

a condition that occurs when electricity current bypasses the intended load, flows back to its source too rapidly and trips fuses, burns wires, and drains batteries.

ground

a connecting body whose electrical potential is zero, to which an electrical circuit can be connected

lock stitch

a crack repair method

oxygen sensor (O2S)

a sensor that consists of a ceramic zirconium thimble, coated on each side with a very thin film of platinum. Once it reaches operating temperature of 600 degrees F (316 C) it begins to function as a very low current battery, producing between 0 - 1.0 volt with the output corresponding to the difference in oxygen between the exhaust and the ambient air. The signal enable the computer to keep the air/fuel mixture as close as possible to stoichiometric mixture. Under normal conditions, the signal should fluctuate above and below 450 millivolts several times a second while the system is in closed loop

Manifold absolute pressure (MAP) sensor

a sensor that measures changes in intake manifold pressure resulting from changes in engine load and speed. The pressure in the intake manifold as referenced to a perfect vacuum. Manifold vacuum is the difference between MAP and atmospheric pressure. For example, in a standard atmosphere (sea level) the pressure is 29.92 inMg, 101 kPa, or 0 inches of vacuum

Intake air temperature (IAT) sensor

a sensor that works by a negative coefficient thermistor, which loses resistance as its temperature goes up When the computer applies its 5 volt reference signal to the sensor, the voltage is reduced through a ground circuit by an amount corresponding to the temperature of the intake air

Engine coolant temperature sensor

a sensor that works by a negative coefficient thermistor, which loses resistance as its temperature goes up (just like the intake air temperature sensor) When the computer applies its 5 volt reference signal to the sensor, the voltage is reduced through a ground circuit by an amount corresponding to the temperature of the engine coolant.

Knock Sensor

a sensor used in engine control system that detects preignition, detonation and knocking. It contains piezoelectric crystal that produces an AC voltage under vibration

keep-alive memory

a series of vehicle battery powered memory locations in the microcomputer that store information on input failure, identified in normal operations for use in diagnostic routines, adapts some calibration parameters to compensate for changes in the vehicle system

program

a set of instructions or procedures that a computer must follow when controlling a system

camshaft

a shaft with eccentric lobes that control the opening of the intake and exhaust valves.

duty cycle

a signal that varies the ratio of on time to off time, resulting in a square wave that can range between zero and 100% or may be high or low, and off may be high or low. In fuel injectors and solenoids, the % of on-time to total cycle time

diode

a simple semiconducting device that permits flow of electricity in one direction but not the other

clear flood mode

a situation in which, under certain circumstances, the computer will shut off all fuel injection , or greatly reduce it. If the throttle position sensor reports wide open throttle (80% open, 3.7 volts or more) and if the engine speed is below 400 rpm, this combination of sensor inputs will be interpreted as an attempt by the driver to ______ _____, that is to blow puddled gasoline off the spark plugs to enable the vehicle to start.

Dry Sleeve

a sleeve, that when installed in a cylinder block, does not come into contact with coolant. Pressed into a cylinder that has been bored, or machined, oversized.

wet sleeve

a sleeve, which when installed in a cylinder block, is exposed to coolant

keyway

a slot cut into a shaft to accept a key

Commutator

a slotted ring located at the end of the armature of a generator or motor. Provides the electrical connection between the armature and brushes

break-in

a slow wearing-in process between two mating part surfaces

valve spring

a small coil spring used to keep the valve closed against the valve seat

valve lifter

a small cylinder that fits into a bore above the cam lobe. It acts on a pushrod and rocker arm to open the valve

fusible link

a smaller gauge wire that is included in an electrical circuit to provide circuit protection the smaller gauge wire will melt when the circuit is overloaded

Babbitt

a soft bearing alloy used in engine bearings

torque sequence

a specified order in which a component's mounting bolts should be tightened

air gap

a specified space between two components e.g. between spark plug electrodes, motor and generator armatures and field shoes

glaze breaker

a spring loaded tool with honing stones that restores the crosshatch surface of a cylinder wall prior to installing new piston rings

rocker stud

a stud that is pressed or threaded into a cylinder head on which the rocker arm is mounted

seat

a surface (usually machine) upon which another part rests

Positive Crankcase Ventilation (PCV)

a system that controls crankcase emissions by using a valve to meter crankcase vapors into the intake manifold

air injection reaction (AIR) system

a system that provides fresh air to the exhaust system under controlled conditions to reduce emissions

fuel injection

a system that sprays fuel directly into the intake air stream

Continuous Ignition system

a system that uses fuel under pressure to modulate or change the injection area

thermistor

a temperature sensitive variable resistor in which the resistance decreases as its temp increases

Ignition Control Module (ICM)

the computer doesn't directly operate the ignition coil because of the comparatively high voltages and currents involved. Instead, it signals this component, when to fire the spark. This component has a power transistor that turns on the ignition primary circuit to charge the coil by building an electromagnetic field around the ferrous core and fires the spark by shutting off he current to the primary circuit, allowing the field to collapse and generate a high voltage spark current in the coil secondary circuit. This component typically includes additional internal circuits to perform other functions such as calculating dwell. *Note: some modern systems have dwell and timing control in the PCM/ECM

electronic control unit (ECU)

the computer in an electronic control system

Bearing Spread

the condition in which the distance across the outside paring edges of the bearing insert is slightly greater than the diameter of the housing bore

Continuity

the condition that exists in a working electrical circuit

Inertia

the constant moving force applied to carry the crankshaft from one firing stroke to the next AKA: the tendency of a body at rest to remain at rest, or of a body in motion , or of a body in motion to remain in motion, unless acted on by an outside force

piston

the cylindrical component that is attached to the connecting rod and moves up and down in the cylinder bore. The top forms the bottom of the combustion chamber. When combustion occurs, it is forced downward in the cylinder, moving the connecting rod, which in turn, rotates the crankshaft

driveability

the degree to which the vehicle operates properly. Includes starting, running smoothly, accelerating and delivering reasonable fuel milage

before top dead center (BTDC)

the degrees of crankshaft rotation just before the piston in a specific cylinder reaches TDC On most vehicles, spark occurs a certain number of degrees of crankshaft rotation ______ ___ ____ ______.

leakdown

the designed discharge within a pressurized body from fully pressurized to non-pressurized, such as within a hydraulic lifter

overbore

the dimension by which a machined hole is larger than the standard size.

valve lift

the distance from the valve seat when the valve is fully open

stroke

the distance the piston moves from TDC to BDC

valvetrain geometry

the dynamic relationship between the rocker arm and valve stem during the time when the valve is opening and closing

lobe

the eccentric part of the camshaft that moves the lifter

starter

the electric motor that is used to start an engine

charge

the electrical current that passes through the battery to restore it to full power; to fill or bring up to the specific level, an AC system with refrigerant; the required amount of refrigerant for an AC system

pressure

the exertion of force upon a surface by an object, fluid, etc., in contact with it, often measured in PSI

dead center

the extreme upper or lower position the crankshaft throw at which the piston is not moving in either direction

exhaust stroke

the final stroke of the four-stroke engine cycle during which the exhaust valve is open and the intake valve is closed, exhausting the combusted gases

intake stroke

the first stroke of a 4-stroke cycle engine in which the intake valve is open and the exhaust valve is closed, during which the downward motion of the piston draws the fuel/air mixture in to the cylinder

corrosion

the gradual wearing away of a metal element due to a chemical reaction

lifter bores

the holes in an engine block that the lifters fit into

main bearing saddle bores

the housings that are machined for main bearings

big end

the large end of the connecting rod that connects to the crankshaft

Pulse Width

the length of time (in milliseconds) that a circuit is energized.

duration

the length of time that a valve remains open, measured in crankshaft degrees

valve duration

the length of time, in degrees of crankshaft rotation, that a valve is open

bearing cap

the lower half of the bearing saddle. It is removable as in main cap or rod cap

housing bore

the machined bore in a block or head where a bearing will be installed

valve seat

the machined surface that the valve face seats against

core (heater core)

the main part of a heat exchanger, such as a radiator, evaporator or heater. Usually made of tubes, surrounded by cooling fins, used to to transfer heat from the coolant to the air

free-play

the measurable travel in a mechanical device between the time force is applied and work is accomplished; looseness in a linkage between the start of application and the actual movement of the device, such as the movement in the steering wheel before the wheels start to turn

normally aspirated

the method by which an internal combustion engine draws air into the combustion chamber. As the piston moves downward in the cylinder, it creates a vacuum that draws air into the combustion chamber through the intake manifold.

torque-turn

the method used to tighten torque-to-yield head bolts. An angle gauge is used to tighten a fastener a specified number of degrees after its is torqued to a foot-pound specification