Engine Performance & Fuel
When checking the ECT sensor with a scan tool, about what temperature should be displayed if the connector is removed from the sensor with the key on, engine off?
-40F (-40C)
Typical TP sensor voltage at idle is about _____.
0.5 volt or 10% of WOT TP sensor voltage
A good fuel pump should be able to supply how much fuel per minute?
0.6 to 0.8 gallons
A typical primary coil resistance specifications usually range from _____ ohms.
1 to 3
Air filters can remove particles and dirt as small as _____.
10 to 25 microns
How quickly can the rocker arms be switched from the low-speed camshaft profile to the high-speed camshaft profile on a Honda equipped with a VTEC system?
100 milliseconds
Most fuel filters are designed to remove particles larger than______.
20 microns
Most TP sensors have how many wires?
3
An IAT is being tested. After the vehicle has been allowed to cool for several hours, a scan tool is used to observe the IAT sensor reading. When compared to the engine coolant temperature (ECT), the two temperatures should be within how many degrees F of each other?
5
Intake charge velocity has to be at least ____ to prevent fuel droplet seperation
50 feet per second
What is the commanded pulse width of the camshaft phaser that results in the desired position?
50%
Typical secondary coil resistance specifications usually range from _____ ohms
6,000 to 30,000
The first fuel filter in the sock inside the fuel tank normally filters particles larger than_______.
70 to 100 microns
A typical IAT or ECT sensor reads about 3000 ohms when tested using a DMM. This resistance represents a temperature of about _____.
70F (20C)
Which statement below is correct?
Most ignition systems work by switching the circuit grounding the ignition coil's primary windings
All these are functions of the air intake system EXCEPT _____.
Silence intake noise Clean the air Act as a flame arrester in case of backfire (ALL CORRECT)
The primary (low voltage) ignition system must be working correctly before any spark occurs from a coil. Which is NOT in the primary ignition circuit?
Spark plug wires
All of the following are approved methods for diagnosing an ECT (Engine Coolant Temperature) sensor EXCEPT ______.
Substituting a variable resistor
Which term describes the principle used to create high voltage from low voltage?
Electromagnetic induction
Which type of port fuel-injection system uses a fuel-temperature and/or fuel-pressure sensor
Electronic returnless systems
Tech A says the 4.2L Trailblazer engine has variable valve timing which changes the point at which the intake valves open and close
False
Air that enters the engine without passing through the airflow sensor is called _____.
False air
All of the following statements are correct EXCEPT _____.
Higher compression engines are less likely to produce NOx emissions
Which type sensor uses a burn-off circuit?
Hot wire MAF sensor
As the load on an engine increases, the manifold vacuum decreases and the manifold absolute pressure ____.
Increases
Which stroke of a four-cycle naturally aspirated engine creates manifold vacuum?
Intake
Which of the following components measures the volume and density of the incoming air?
Mass Airflow Sensor
Which is NOT a purpose or function of the MAP sensor?
Measures engine speed
Which of the following is correct?
Naturally aspirated engines use atmospheric pressure to force air into the combustion chamber.
Most variable camshaft systems use ____ to control camshaft position.
Oil pressure
Boost pressure is generally measured in ____.
PSI
The _____ sends a pulse signal to an electronic ignition module.
Pickup coil
The upper portion of a two part intake manifold is often called the _______.
Plenum
Dampeners are used on some fuel rails to ______.
Reduce noise
Why are some fuel rails rectangular in shape?
Reduces noise
What service operation is MOST important on engines equipped with a turbocharger?
Regular oil changes
Two types of superchargers include ____.
Roots type and centrifugal
A fuel injection system that does not use a sensor to measure the amount (or mass) of air entering the engine is usually called a(an) _____ type of sensor.
Speed density
Which fuel-injection system uses the MAP sensor as the primary sensor to determine the base pulse width?
Speed density
What type of device is used in a typical idle air control?
Stepper motor
All of the following statements are correct EXCEPT _____.
Supercharging often results in high emissions during deceleration and idle
Which sensor has the greatest influence on injector pulse width besides the MAF sensor?
TP
Which sensor is generally considered to be the electronic accelerator pump of a fuel injected engine?
TP sensor
A heated air intake system is usually necessary for proper cold-engine driveability on ______.
Throttle body fuel injection systems
Why is a vacuum line attached to a fuel-pressure regulator on many port fuel-injected engines?
To create an equal pressure drop across the injectors
Why do many port fuel injected engines use long intake runners?
To increase low RPM torque
What is the purpose of an intercooler?
To reduce the temperature of the air entering the engine
The ignition system is usually split into how many different section or circuits?
Two
Tech A says that the fuel-pump relay is usually controlled by the PCM. Tech B says that a TBI injector squirts fuel above the throttle plate. Which technician is correct?
Both Technicians
The use of variable valve timing allows the elimination of the ____ on some engines.
EGR Valve
The typical MAF reading on a scan tool with the engine at idle speed and normal operating temperature is _____.
3 to 7 grams per second
On engines that have variable cam timing on the intake cam only, the cam is advanced at lower speeds. This causes the intake valve to close _____ to improve low RPM torque
Earlier
Which valve is used on a factory supercharger to limit boost?
A bypass valve
What is annealing?
A heat-treating process that takes out the brittle hardening of a cast iron casting.
On some engines, what holds the cam in position during cranking
A locking pin
A typical MAP sensor compares the vacuum in the intake manifold to ______.
A perfect vacuum
Which airflow sensor has a dampening chamber?
A vane airflow
Where is the fuel-pressure regulator located on a vacuum-biased port fuel-injector system?
At the outlet of the fuel rail
What type of relief valve is used on a turbocharged engine is noisy?
A BOV A dump valve
The frequency output of a digital MAP sensor is reading 114 Hz. What is the approximate engine vacuum?
15 in. Hg
Which statement is false?
Absolute pressure is equal to barometric pressure plus intake manifold vacuum
A MAF sensor on a General Motors 3800 V-6 is being tested for contamination. Tech A says that the sensor should show over 100 grams per second on a scan tool display when the accelerator is depressed to WOT (wide open throttle) on a running engine. Tech B says that the output frequency should exceed 7000 Hz when the accelerator pedal is depressed to WOT on a running engine. Which technician is correct?
Both Technicians
A MAP sensor is being tested. Tech A says that many MAP sensors also act as a barometric pressure sensor when the ignition switch is first turned on. Tech B says on may MAP sensors the signal voltage should increase when the vacuum at the sensor decreases. Which technician is correct?
Both Technicians
Tech A says that a MAF sensor actually measures the density and amount of air flowing into the engine, which results in accurate engine control. Tech B says that a hot wire MAF sensor uses the electronics in the sensor itself to heat a wire 70C above the temperature of the air entering the engine. Which technician is correct?
Both Technicians
Tech A says that the 3 wires on the TP sensor include a 5-volt reference voltage from PCM, plus the signal wire to PCM, and ground. Tech B says that the TP sensor is used by the PCM to determine torque converter engagement and transmission shift points. Which technician is correct?
Both Technicians
Two technicians are discussing testing MAP sensors. Tech A says that voltage on a General Motors vehicle at idle should be about 1.0 volt. Tech B says MAP sensor frequency on a Ford vehicle at idle should be about 105 - 108 Hz. Which technician is correct?
Both Technicians
Two technicians are discussing the term "turbo lag". Tech A says that it refers to the delay between when the exhaust leaves the cylinder and when it contacts the turbine blades of the turbocharger. Tech B says it refers to the delay in boost pressure that occurs when the throttle is first opened. Which technician is correct?
Both Technicians
How are most superchargers lubricated?
By an internal oil reservoir
How are most turbochargers lubricated?
By engine oil under pressure through lines from the engine
Which design of MAP sensor produces a frequency (digital) output signal?
Capacitor-capsule
Dirt can affect all of these sensors, EXCEPT ______.
Cold wire MAF (mass airflow sensor)
When measuring the output signal of a MAP sensor on a General Motors vehicle, the digital multimeter should be set to read _______.
DC Volts
Active fuel management on GM vehicles was initially called ______.
Displacement on Demand
Two technicians are discussing Karman Vortex sensors. Tech A says that they contain a burn-off circuit to keep them clean. Tech B says that they contain a movable vane. Which technician is correct?
Neither Technician
A reluctor is a ______.
Notched ring or pointed wheel
Tech A says that MAP sensors use a 5-volt reference voltage from the PCM. Tech B says the MAP sensor voltage will be higher at idle at high altitudes compared to when the engine is operating near sea level. Which technician is correct?
Technician A only
Tech A says that a MAF sensor is a high-authority sensor and is responsible for determining the fuel needs of the engine based on the measured amount of air entering the engine. Tech B says that a cold wire MAF sensor uses the electronics in the sensor itself to heat a wire 20C below the temperature of the air entering the engine. Which technician is correct?
Technician A only
Tech A says that pressure below atmospheric pressure is called vacuum and is measure in inches of Mercury (Hg). Tech B says that a manifold absolute pressure (MAP) sensor used a low vacuum in the sensor to determine the pressure. Which technician is correct?
Technician A only
Tech A says that the 3 wires on the TP sensor include a 5-volt reference voltage from the PCM. Tech B says that a TP sensor is a three-wire variable resistor called a rheostat. Which technician is correct?
Technician A only
Two technicians are discussing a poorly running engine. There are no diagnostic trouble codes. When the MAF sensor is unplugged, the engine runs better. Tech A says that this means the MAF is supplying incorrect air flow information to the PCM. Tech B says that this indicates the PCM is defective. Which technician is correct?
Technician A only
Two technicians are discussing testing MAP sensors. Tech A says that the MAP sensor should be replaced if anything comes out of the sensor when the vacuum hose is removed from the sensor. Tech B says that the injector pulse width should increase when vacuum to the MAP sensor is increased. Which technician is correct?
Technician A only
Tech A says that a stuck-open wastegate can cause the engine to burn oil. Tech B says that a clogged PCV system can cause the engine to burn oil. Which technician is correct?
Technician B only
Tech A says that the TP sensor signal voltage should be about 0.5 volt at idle and increase to about 2.5 volts at wide-open throttle (WOT). Tech B says that a TP sensor can be tested using a DMM (digital multimeter), DSO (Digital storage oscilloscope), or scan tool. Which technician is correct?
Technician B only
Tech A says that the port fuel-injection injectors operate using 5 volts from the computer. Tech B says that the sequential fuel injectors all use a different wire color on the injectors. Which technician is correct?
Technician B only
Which sensor has a switch that controls the electric fuel pump?
VAF
All of these are factors in calculating required airflow EXCEPT _____.
Volumetric efficiency Engine displacement Engine speed (RPM) (ALL CORRECT)
Which of these is correct regarding volumetric efficiency?
Volumetric efficiency is expressed as a percentage
Which statement below is correct?
A spark tester requires more voltage than a spark plug to fire
The secondary ignition circuit can be tested using _____.
An Ohmmeter An Ammeter
A fuel pump is being replaced for the third time. Tech A says that the gasoline could be contaminated. Tech B says that wiring to the pump could be corroded. Which technician is correct?
Both Technicians
Exhaust passages are included in some intake manifolds. Tech A says that the exhaust passages are used for exhaust gas re-circulation (EGR) systems. Tech B says that the exhaust heat is used to warm the intake charge on some engines equipped with a throttle-body-type fuel-injection system. Which technician is correct?
Both Technicians
Tech A says that a cracked exhaust manifold can affect engine operation. Tech B says that a leaking lower intake manifold gasket could cause a vacuum leak. Which technician is correct?
Both Technicians
Tech A says that a defective crankshaft position sensor can cause a no-spark condition. Tech B says that a faulty ignition control module can cause a no-spark condition. Which technician is correct?
Both Technicians
Tech A says that a defective spark plug wire of boot can cause an engine misfire. Tech B says that a tracked ignition coil can cause an engine misfire. Which technician is correct?
Both Technicians
Tech A says that a distributor rotor can burn through and cause an engine misfire during acceleration. Tech B says that a defective spark plug wire can cause an engine misfire during acceleration. Which technician is correct?
Both Technicians
Tech A says that a vehicle equipped with an ASD relay only have power at the ignition coil when the engine is cranking or running. Tech B says that a defective ASD relay could cause a no-start condition. Which technician is correct?
Both Technicians
Tech A says that some intake manifolds are plastic. Tech B says that some intake manifolds are constructed in tow parts or sections: upper and lower. Which technician is correct?
Both Technicians
Tech A says that the ECT and IAT sensors can be tested visually, as well as by using a digital multimeter or a scan tool. Tech B says that the ECT sensor is a high-authority sensor at engine startup and is used for open-loop control, as well as idle speed. Which technician is correct?
Both Technicians
Tech A says that the firing line shows the voltage that is required to fire the spark plug. Tech B says that the spark line shows the duration of the spark inside the cylinder. Who is correct?
Both Technicians
Technician A says that other temperature sensors that operate like the ECT include the Transmission Fluid Temperature (TFT), and Cylinder Head Temperature sensor. Tech B says that all temperature sensors increase in resistance as the temperature decreases. Which technician is correct?
Both Technicians
Two techs are discussing a no-start (no-spark) condition. Tech A says that an open pickup coil could be the cause. Tech B says that a defective Ignition Control Module (ICM) could be the cause. Which technician is correct?
Both Technicians
Two techs are discussing distributor ignition. Tech A says that the pickup coil or optical sensor in the distributor is used to pulse the ignition module (igniter.) Tech B says that some distributor ignition systems have the ignition coil inside the distributor cap. Which technician is correct?
Both Technicians
What sensors are used by the PCM to determine the best position of the camshafts for maximum power and lowest possible exhaust emissions?
Camshaft position (CMP) sensor Engine speed (RPM) Crankshaft position (CKP) sensor
The ignition module has direct control over the firing of the coil(s) of an EI system. Which component(s) triggers (controls) the module
Computer Crankshaft sensor Pickup coil
The intake manifold of a port fuel-injected engine ______.
Contains only air
Why are the EGR gasses cooled before entering the engine on some engines?
Cool exhaust gas is more effective at controlling NOx emissions.
The amperage draw of an electric fuel pump is higher than specified. All of the following are possible causes EXCEPT:
Corroded electrical connections at the pump motor
When testing an ECT sensor on a vehicle, a digital multimeter can be used and the signal wire back probed. What setting should the technician use to test the sensor?
DC Volts
If the transmission fluid temperature (TFT) sensor indicates cold automatic transmission fluid temperature, what would the PCM do to the shifts?
Delayed shift points and torque converter clutch disabled
An ion-sensing ignition system allows the ignition system itself to be able to ____.
Detect spark knock Detect misfire Detect rich or lean air-fuel misture
Which is NOT a function of a TP sensor
Determining rich and lean air-fuel mixtures
Coil polarity is determined by the _______.
Direction of rotation of the coil windings
HEI and EIS are examples of
Distributor ignition systems
The sensor that most determines fuel delivery when a fuel injected engine is first started is the _____.
ECT (Engine Coolant Temperature) sensor
Which of the following components provides the engine control computer with engine coolant temperature information?
ECT sensor
To reduce oxides of nitrogen (NOx) exhaust emissions, which camshaft is varied?
Exhaust camshaft only
A waste-spark-type ignition system ______.
Fires two spark plugs at the same time Fires one spark plug with straight polarity Fires one spark plug with reverse polarity
Which sensor produces a square wave signal?
Hall Effect Sensor Optical Sensor
The Sensor that measures the temperature of the air being drawn into the engine is called which of these?
IAT
The ignition system pickup coil or trigger is usually connected to which device?
Ignition module
What happens to the voltage measured at the ECT sensor when the thermostat opens?
Increases slightly
Because of _____, an ignition coil cannot be fully charged (reach magnetic saturation) until after a delay of about 10 ms.
Inductive reactance
If it is tripped, which type of safety device will keep the electric fuel pump from operating?
Inertia switch
To increase engine performance, which camshaft is varied?
Intake camshaft only
Which statement is correct?
Long intake runners are good for low-RPM torque Some engines use a variable intake runner design to improve engine efficiency. Short intake runners are good for high-RPM torque (ALL CORRECT)
A fuel filter has been accidentally installed backwards. What is the most likely result?
Lower power at higher engine speeds and loads
Which of these sensors does the TP sensor backup if the PCM determines that a failure has occured
MAF sensor MAP sensor
Which of the following is correct?
Many exhaust systems are tuned to reduce noise and optimize flow. Many exhaust systems have heat shields to protect the spark plugs and wires. Exhaust manifolds must be able to slide on the cylinder head slightly as they expand due to high heat.
The pulse generator _____.
Signals the electronic control unit (module)
A technician attaches one lead of a digital voltmeter to the ground terminal of the TP sensor and other meter lead to battery negative terminal. The ignition is turned on, engine off and the meter displays 37.3mV. Tech A says that this is the signal voltage and is a little low. Tech B says that the TP sensor ground circuit has excessive resistance. Which technician is correct?
Neither Technician
Tech A says that the EGR system helps to control nitrous oxide (N2O). Tech B says that all engines use an EGR valve to lower combustion temperature. Which technician is correct?
Neither Technician
What prevents the fuel pump inside the fuel tank from catching the gasoline on fire?
No air is around the motor brushes
When testing an ECT sensor with the connector disconnected, the technician should select what position on the DMM (digital multimeter)?
Ohms
Which of the following is correct?
One gallon of gasoline produces a gallon of moisture during complete combustion.
A TP sensor is what type of sensor?
Potentionmeter
How is the camshaft actuator controlled?
Pulse width modulated (PWM) signal
Variable valve timing is used to ___.
Reduce exhaust emissions Increase engine perfomrance
The following statements are all correct EXCEPT _____.
Resistance of the primary ignition coil winding's should be infinite
Variable valve timing can be found on which type of engine?
SOHC Cam-in-block DOHC
Fuel lines are constructed from_____.
Seamless steel tubing Nylon plastic
Which wire on a TP sensor should be back probed to check for a voltage signal to the PCM?
Signal wire
Tech A says that header-type exhaust manifolds produce less back pressure than do most cast-iron exhaust manifolds. Tech B says that only cast-iron exhaust manifolds are used on production vehicles. Which technician is correct?
Technician A only
Tech A says to check for spark from the ignition coil first when diagnosing a no-start condition. Tech B says to check the engine speed sensor first to diagnose a no-spark condition. Which technician is correct?
Technician A only
Tech A says that active fuel management is only used on large V8's. Tech B says that active fuel management increases fuel economy. Which technician is correct?
Technician B only
Tech A says that all temperature sensors are NTC devices that decrease in resistance as the temperature increases. Tech B says that some vehicle manufactures use a stepped ECT circuit inside the PCM to broaden the accuracy of the sensor. Which technician is correct?
Technician B only
Tech A says that an engine will not start and run if the ignition coil is tracked. Tech B says that the engine will not start if the crankshaft position sensor fails. Which technician is correct?
Technician B only
Tech A says that fuel pump modules are spring-loaded so that they can be compressed to fit into the opening. Tech B says that they are spring-loaded to allow for expansion and contraction of plastic fuel tanks. Which technician is correct?
Technician B only
Tech A says that primary winding's should have higher resistance. Tech B says that secondary winding's should have higher resistance. Which technician is correct?
Technician B only
Tech A says that the coil primary has more winding. Tech B says that the coil secondary has more winding's. Which technician is correct?
Technician B only
Tech A says that the primary and secondary ignition systems are never connected. Tech B says that the primary and secondary ignition winding are connected in some ignition coils. Which technician is correct?
Technician B only
Tech A says that the resistance of a pickup coil cannot be tested. Tech B checks for AC Voltage from the pickup coil when cranking the engine. Which technician is correct?
Technician B only
Tech A says the the Helmholtz resonator is used to speed up incoming air into the intake manifold. Tech B says that the Helmholtz resonator is used to reduce intake noise. Which technician is correct?
Technician B only
Tech A says to only use new exhaust manifold gaskets if they were used originally. Tech B says to always use new exhaust manifold gaskets to allow for the slight warpage of the exhaust manifold. Which technician is correct?
Technician B only
Tech A says to use a normal spark plug when checking for spark. Tech B says that a spark tester should be used to check for spark. Which technician is correct?
Technician B only
Two techs are discussing a stepped ECT circuit. Tech A says that the sensor used for a stepped circuit is different than one used for a non-stepped circuit. Tech B says that a stepped ECT circuit uses different internal resistance inside the PCM. Which technician is correct?
Technician B only
Two techs are discussing the IAT sensor. Tech A says that the IAT sensor is more important to the operation of the engine (higher authority) than the ECT sensor. Tech B says that the PCM will add fuel if the IAT indicates that the incoming air temperature is cold. Which tech is correct?
Technician B only
After a TP sensor has been tested using the MIN/MAX function on a DMM, a reading of zero volts is displayed. Which of these does this reading indicate?
The TP sensor is open at one point during the test
After a TP sensor has been tested using the MIN/MAX function on a DMM, a reading of 5 volts is displayed. What does this reading indicate?
The TP sensor signal is shorted to 5-volt reference
If the engine oil is not changed regularly, what is the most likely fault that can occur to an engine equipped with variable valve timing (VVT)?
The filter screens on the actuator control valve become clogged
Which statement is correct?
With port fuel injection, fuel is injected near the intake valve.
