ASE A1 ENGINE REPAIR
What does white carbon deposits indicate on a spark plug?
A lean fuel condition
What's a returnless fuel system?
A returnless system have no return line which eliminates emission problems by consuming fuel in fuel rail. The assembly itself is on the fuel pump housing inside the tank.
What's the indication if the vacuum gauge reads a steady 17 in. Hg to 22 in. Hg?
A steady reading of 17 in. Hg to 22 in. Hg indicates a normal running engine.
Tech A says only the upper front main bearing is worn, belt adjusted too tight is indicated. Tech B says when an engine with a knock is disassembled, connecting rod bearing(s) closest to the oil pump will show the most wear. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
A. A tight belt will cause wear to front upper main bearing. When an oil supply problem has resulted in knock, the bearings furthest from the oil pump will wear first.
After diagnosing and replacing the cooling system's water pump, the vehicle engine continues to overheat. Which of these is the MOST likely cause? A. An air pocket in the system. B. Leaking head gasket C. Faulty replacement water pump D. The radiator
A. An air pocket in the system.
Extensive engine bearing damage has been observed during disassembly. Tech A says internal engine coolant leak could be the cause. Tech B says stuck-closed oil pressure relief valve could be the cause. A. Tech A B. Tech B C. Both A and B D. Neither A or B
A. An internal engine coolant leak Coolant contamination oil can bearing damage.
A ridge has formed on an engine block just above the piston ring's travel. Which of the following is used to remove the ridge? A. A cylinder ridge reamer B. A flexible beaded hone C. Both A and B D. Neither A or B
A. Cylinder ridge reamer
An engine has a light metallic knocking noise during light engine loads, however, when the cylinder with the noise is disabled during a cylinder balance test, the sound diminishes. Technician A says that the noise is caused by excessive connecting rod bearing clearance. Technician B says that the noise is caused by excessive piston-to-wall clearance. Who is right? A. Technician A only B. Technician B only C. Both A and B D. Neither A or B
A. Excessive connecting rod bearing clearance When eliminating ignition or injection to a cylinder with rod knock, sound diminishes. Unlike connecting rod bearing noise, piston rod does not quiet down and may in fact grow louder when you eliminate ignition or fuel injection to that cylinder.
Of the following spring measurements, which would NOT require spring replacement if the measurement is not within specification? A. Installed height B. Pressure C. Free height D. Squareness
A. Installed height Spring installed height can be corrected by installing shims between valve spring and cylinder. If spring free height, squareness or pressure is not within specification, spring must be replaced.
Which of the following is NOT a method of correcting excessive valve stem to guide clearance? A. Knurling the valve stem B. Knurling the guide C. Reaming for oversize D. Guide replacement
A. Knurling the valve stem. A valve stem is hardened and CANNOT be knurled.
Engine gradually overheats at cruising speeds but returns to normal at idle. Both of the electric cooling fans are function correctly. Which of the following is MOST likely causing this condition? A. A restriction in the radiator B. Stuck closed fan relay C. Faulty radiator cap D. A leak in the cooling system
A. Restriction in the radiator - Rust can clog radiator's internal passages, altering the flow of coolant, causing the engine to over heat. Inspect the radiator for external damage and use an infrared thermometer to find internal restrictions.
Engine gradually overheats at cruising speeds but returns to normal idle. Both engine's electric fan are function correctly. Which of the following is MOST likely causing this condition? A. Restriction in radiator B. Stuck closed fan relay C. Faulty radiator cap D. Leak in the cooling system
A. Restriction in the radiator. Radiator alters flow of coolant causing engine to overheat. Inspect the radiator for external damage and use an infrared thermometer to find internal restrictions.
Camshaft lift is defined as: A. Distance the valves are open B. Height of the lobes on the camshaft C. Time the valves stay closed D. Time the valves stay open
B. Height of the lobes on the camshaft
A longitudinal engine makes a loud, whirling noise that gets louder when the engine is revved. Which of the following is causing this condition? A. A faulty viscous fan clutch B. A worn accessory belt C. A weak electric cooling fan motor D. A cracked fan blade
A. Seized viscous fan clutch makes a whirring noise because the clutch is locked and not slipping, spinning the fan blades at engine speed at all times.
Tech A says that deep gouge in a cylinder bore can be repaired by installing a sleeve. Tech B says a crack in a cylinder bore requires that the block be replaced. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
A. Sleeve can be used to repair a damaged or cracked cylinder bore.
After a cooling system flush was performed, there's very little heat inside the passenger compartment. Tech A says air trapped in engine cooling system could be the cause. Tech B says use an incorrect coolant mixture could be the cause. A. Tech A B. Tech B C. Both A and B D. Neither A or B
A. Tech A Air introduced into cooling system during flush creates an air pocket in system that prevents proper coolant flow.
Tech A says piston rings installed upside down will cause increased oil consumption. Tech B says rings installed upside down will cause piston ring land damage. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
A. Tech A Piston rings are designed with slight taper on ring face to scrape oil off cylinder. When installed upside down, rather than scraping oil down and off the walls, scrapes oil up into combustion chamber where it's burned, causing increase oil consumption. Installing rings upside down does not change ring land clearance, rings lands will not be affected.
Two technicians are discussing an engine with a collapsed radiator hose. Tech A says this is caused by a faulty radiator cap. Tech B says this is caused by insufficient coolant level. Who is correct? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
A. Tech A Radiator cap controls the expansion and provides constant pressure on the system. It allows the engine's coolant to expand and contract without allowing air to enter the cooling system. Upper seal seals and protects system all the time. After engine warms and system pressure reaches the caps rated pressure, pressure spring compresses and pressurized coolant flows into reservoir (overflow tank). Allowing the expansion of heated fluid.
Tech A says excessive grinding of valve faces and seats allows the valve tips to move too far away from their spring seats. Tech B says grinding the stem tips helps to correct minor changes in valve spring installed height. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
A. Tech A Step tip height increase with valve or seat grinding. Grinding stem tips can change step tip height, but no effect on valve spring installed height. Measurement is controlled by height of keeper grooves above spring seat of the head.
Tech A engine cylinders wear MOST at the top of the ring travel. Tech B says the difference in cylinder bore measurements taken parallel and perpendicular to the crankshaft will indicate cylinder bore taper. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
A. Tech A Most wear to the engine cylinder is at the top where ring loading is at its greatest.
Installed height of a valve spring is greater than specified. Tech A says that a worn valve seat could be the cause. Tech B says that the weak valve spring could be the cause.
A. Tech A - Worn valve seat allows valve to seat deeper causing higher installed height.
An OHC engine has recently had the cylinder head replaced. The engine runs rough and stumbles. Tech A says this may be caused by incorrect valve lash adjustment. Tech B says that only in-block camshafts require valve lash adjustments. Who is correct? A. Tech A B. Tech B C. Tech A and B D. Neither Tech A or B
A. Tech A - incorrect valve lash adjustment
Tech A says insufficient hydraulic lifter preload results in excessive valve train noise. Tech B says excessive hydraulic lifter preload results in a high intake manifold vacuum. Who is correct? A. Tech A B. Tech B C. Tech A and B D. Neither A or B
A. Tech A Insufficient preload results in valve train noise, excessive preload results in low manifold vacuum and rough idle.
Two technicians are discussing the camshaft in a V8 engine. Tech A says to use the an outside micrometer to measure the diameter of a camshaft journal. Tech B says camshaft spins twice for every one revolution of the crankshaft. Who is correct? A. Tech A B. Tech B C. Tech A and B D. Neither Tech A or B
A. Technician A - use an outside micrometer to measure the diameter of a camshaft journal.
Tech A says valve spring installed height is measured from the outer edge of the valve spring retainer to the pocket in the cylinder head. Tech B says that too thin of a valve margin will not effect its operating temperature. Who is correct? A. Tech A B. Tech B C. Both Tech A and B D. Neither A or B
A. Technician A - valve spring installed height is measured from the outer edge of the valve spring retainer to the pocket in the cylinder head. Note: Check valve spring length with a caliper. Check valve springs installed height from base or pocket in the head to the bottom of the retainer. If height is excessive, add appropriate shim to bring the spring back to it's proper tension. Any short springs (1/16 inch) should be replaced. Tension can be checked with a valve spring tester.
What is RTV (Room Temperature Vulcanizing)?
An aerobic sealant meaning that it cures in the presence of air.
All of the following can result from resurfacing a cylinder block EXCEPT: A. Change in camshaft timing on an overhead camshaft engine B. Change in alignment between the cylinder heads and intake manifold on V8 engine C. Decreased compression D. Change in valvetrain geometry on pushrod engine
C. Decreased compression Resurfacing the block will decrease the deck height (distance from top of the piston at TDC on the top of the block and raise compression)
An engine is losing coolant. A radiator pressure tester is installed on the neck of the radiator while engine is cold. After starting the engine, the pressure on the gauge quickly rises to 19 psi. Which of the following is causing this test result? A. Acidic engine coolant B. Cylinder head gasket is leaking C. There's an air pocket in the coolant system D. The pressure is normal
B. Cylinder head gasket is leaking Aluminum heads warp from overheating, cracks can form in cylinder head or engine block. A leaking head gasket allows combustion into the coolant jacket, increasing system pressure. Coolant leaking into combustion chamber burns white and results white-gray exhaust smoke.
An engine's aluminum thermostat housing has corroded prematurely and is leaking coolant. Which of the following is MOST likely causing this condition? A. Engine overheating B. Electrolysis C. A leaking radiator hose D. A faulty thermostat
B. Electrolysis - causes corrosion in cooling system. As coolant breaks down it becomes acidic. It acts as catalyst for electrical current. Small amount of electrical current can flow through coolant corroding the lesser metal, more often the aluminum such as the water pump and engine's coolant outlet.
Customer states engine is sluggish at acceleration. During test, vacuum gauge reads 20 in. Hg with the transmission in PARK. During vehicle test drive, vacuum measures near 0 in. Hg at WOT (wide open throttle). During light cruising speed at 2000 RPM, vacuum measures a steady 12 in. Hg. Which of these could be the cause? A. High fuel pressure B. Excessive exhaust backpressure C. Intake manifold vacuum leak D. Blown head gasket
B. Excessive exhaust backpressure Excessive exhaust backpressure prevents engine from breathing properly because it can expel exhaust. Decreased in engine performance and low vacuum readings at WOT speeds.
Tech A says that a cylinder should be bored within 0.001 in of final size. Tech B says says plateau finish on cylinder bore will help seat the piston rings. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
B. Follow normal honing, some manufacturers recommend a plateau finish in bore. Plateau honing levels off the peaks left in bore surface from honing. Final polishing step forms flat plateau areas between grooves or valleys of crosshatch. Plateau surface retains oil and allows faster ring seating while reducing ring and cylinder wear. When cylinder is bored, 0.0025 - 0.003 in cylinder material is left for finish honing to final size. It's necessary to completely remove the rough finish left by the boring tool.
Timing cover is being installed using synthetic rubber gasket. Tech A says that a 1/8 in to 3/16 in wide bead of sealer should be applied along the length of the cover flange and block surface. Tech B says gasket must be installed against a perfectly clean and dry surface. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
B. Gasket sealer must NOT be used on synthetic rubber gaskets. It acts like a lubricant causing the gasket to slip and leak.
Customer states that the engine overheats at idle but not at highway speeds. Which of these could be the cause? A. Plugged radiator B. Inoperative cooling fan C. Shorted coolant sensor D. Stuck open thermostat
B. Inoperative cooling fan Inoperative cooling fan prevents heat transfer at low vehicle speeds, but airflow at highway speeds is sufficient to cool the radiator.
During diagnosis, technician observes that the engine vacuum is 12 in. Hg with the engine warm and idling. Which of the these could be the cause? A. A plugged air filter B. Retarded valve timing C. Low fuel pressure D. Cracked exhaust manifold
B. Retarded valve timing Retarded valve timing will affect the engine to breath and cause low engine vacuum.
Tech A says camshaft duration is the distance the camshaft's lobe lifts the valve off the valve seat and into the cylinder. Tech B says valve overlap occurs when the intake and exhaust valves remain open at the same time. Who is correct? A. Tech A B. Tech B C. Tech A and B D. Neither A or B
B. Tech B
A cylinder leak-down test is being performed on an engine. Tech A says that the engine should be cold. Tech B says that the piston should be at TDC on compression stroke. A. Tech A B. Tech B C. Both Tech A and B D. Neither A or B
B. Tech B - Cylinder leak down test MUST be performed when the engine is at operating temperature. - Piston should be at TDC (Top Dead Center) on compression stroke
Tech A says shim can be used to rotate the valve spring. Tech B says a shim can be used to correct installed spring height. Who is correct? A. Tech A B. Tech B C. Both A and B D. Neither A or B
B. Tech B A flat shim when placed under the valve spring to adjust installed height to specifications, in response of changing valve height caused by valve and seat machining.
Tech A says a flex flan will increase its pitch at higher engine speeds. Tech B says a viscous fan clutch contains a silicon based fluid and should be checked for leaks. Who is correct? A. Tech A B. Tech B C. Tech A and B D. Neither A or B
B. Viscous fan clutch contains a silicon based fluid and should be checked for leaks.
A new overhead camshaft will not rotate by hand when installed in a cylinder head. Which of these could be the cause? A. Insufficient valve spring installed height B. A warped cylinder head C. Excessive cam bearing clearance D. Insufficient valve stem height
B. Warped cylinder head Warped cylinder head will cause misalignment of camshaft main bearing journals which prevents camshaft from turning.
Tech A says engine should be accelerated when checking vacuum advance. Tech B says engine should be accelerated when checking centrifugal advance. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
B. Weights and springs in a centrifugal advance mechanism are calibrated to advance ignition timing as engine speed increases, therefore engine must be accelerated when checking for centrifugal advance.
Which of the following results in low oil pressure? A. Stuck closed oil pressure relief valve B. Worn crankshaft bearings C. Restriction in oil passage D. Clogged oil pressure relief valve
B. Worn crankshaft bearings Worn crankshaft, camshaft and rod bearings results to low oil pressure. They're different specifications and tolerances according to vehicle application. It's usually no more than .001 inch off the diameter of the bearing.
All of the following can cause low oil pressure EXCEPT: A. Diluted engine oil B. Worn pistons C. Excessive bearing clearance D. Clogged oil pump pickup
B. Worn pistons Worn pistons can cause noise and accelerate ring and bore wear, but it will not cause low oil pressure.
A vacuum gauge connected to the intake manifold of an engine running at idle. Pointer on the gauge fluctuates rapidly but steadies as speed is increased. Test results indicates: A. Leaking intake manifold gasket B. Worn valve guides C. Late ignition timing D. A weak valve spring
B. Worn valve guides Worn valve guides will cause the gauge needle to fluctuate rapidly at idle but steady as engine speed is increased.
A vehicle with a 4-cylinder engine is towed into a shop with "no crank" complaint. Amperage meter in the illustration is connected to the circuit with KEY ON to the START position. Which of these could be the cause of the reading shown? A. A weak battery B. Poor ground connection C. Seized engine D. An open starter solenoid
C. A seized engine will cause an abnormally high amperage draw.
Tech A says valve lash should be adjusted with piston in cylinder being adjusted at TDC on compression stroke. Tech B hydraulic lifters should be adjusted to zero lash. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
C. Both A and B Adjust valve lash for one cylinder's cam lobes, rotate crankshaft so piston is at TDC on compression stroke. This will position intake and exhaust valve lifters or OHC cam followers on base circle of their respective cam lobes. Hydraulic lifters should be adjusted until zero lash is reached, then turn additional number of turns (3/4 - 1 1/2 turns).
Tech A says a flat-tappet hydraulic lifter rotates during operation. Tech B says of the lifter should be convex. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
C. Both A and B Flat tappet face is convex, cam lobe is slightly tapered (about 0.0005 - 0.0007 in) and lifter bore is offset to make the lifter rotate during operation. Rotation is essential because it spreads wear over greater surface are. If lifter fails to spin, it will destroy itself and its cam lobe.
Tech A says a defective harmonic balancer can cause inaccurate ignition timing readings. Tech B says that harmonic balancer can cause a broken crankshaft. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
C. Both A and B Outer ring on a defective harmonic balancer can slip, causing inaccurate ignition timing readings. A broken crankshaft can also result from an incorrect or defective balancer.
A metallic knocking sound hear behind the engine's harmonic balancer. An oil pressure test indicates oil pressure is below specifications. Tech A says engine's main bearing inserts should be inspected for wear. Tech B says worn thin crankshaft thrust bearing will cause this condition. Who is correct? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
C. Both Tech A and B
Technician A says an engine's main bearing insert has a hole that must align with the matching bores oil supply hole. Technician B says the crankshaft bore alignment can be checked with a feeler gauge and a straightedge. Who is correct? A. Tech A B. Tech B C. Both Tech A and Tech B D. Neither Tech A or B
C. Both Tech A and B
Two technicians are discussing an engine that suffers from repeated spark plug failure. Tech A says a hot spark plug with too high of a heat range may result in detonation. Tech B says a cold spark plug with too low of a heat range may foul prematurely. Who is correct? A. Tech A B. Tech B C. Both Tech A and B D. Neither A or B
C. Both Tech A and B A too high of a heat range from a spark plug can lead to pinging, detonation, and preignition. A cold spark plug helps with pre-ignition but can get dirty and foul out sooner, especially if vehicle is driven short distances or frequently idled.
Tech A says blown head gasket results coolant entering the combustion chamber. Tech B says a blown head gasket could result in contaminated milky brown engine oil. Who is correct? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
C. Both Tech A and B - Coolant enters crankcase through blown head gasket or leaking manifold jacket and mixes with the oil. Results the oil turning milky brown and can be seen from the dipstick and accumulate around the oil and radiator fill neck. Also when coolant enters the combustion chamber coolant will vaporize, results to a white-colored exhaust smoke.
An engine suffers from detonation. Tech A this may be caused by a defective EGR valve. Tech B says advanced ignition timing can cause this condition. Who is correct? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
C. Both Tech A and Tech B
All of the following statements about batteries are true EXCEPT: A. Fully charged battery should be specific gravity of 1.260 B. If open circuit voltage is less than 12.4 volts, charge the battery at a slow rate C. A battery is load tested to one third it's CCA rating for 15 seconds D. End of load test, battery voltage must be 9.6 volts or more
C. During load test, battery should be loaded to one-half its CCA rating for 15 seconds
All of following are ways to clean an aluminum engine EXCPET: A. Cold solvent tank B. Carburetor cleaner C. Hot caustic tank D. Pyrolytic oven
C. Hot caustic tank will damage the aluminum.
When a cylinder head is disassembled, the stem height on one valve is found to be too high. Which of the following can correct this? A. Regrind the valve B. Regrind the valve seat C. Install a new valve seat D. Install a shim
C. Install a new valve seat Installing a new valve seat will position the valve lower in the head and reduce stem height.
Scan data shown was observed during diagnosis of vehicle for illuminated MIL light and a stored "System Too Lean - Bank 1" DTC. Which of these could be the cause? A. Restricted exhaust B. Restricted air filter C. Leaking intake gasket D. Weak fuel pump
C. Leaking intake gasket Fuel trims indicate lean condition at idle and normal off idle. Characteristic of un-metered air entering intake system.
A vehicle briefly blows blue-gray exhaust smoke from its tailpipe only in the morning or after it's been sitting for a while. Which of the following causing the condition? A. Leaking cylinder head gasket B. Leaking valve stem seals C. A leaking fuel injector D. Worn piston rings
C. Leaking valve stem seals
A spark plug's electrode covered with "thick black" carbon deposits. Which of these could be the cause? A. Engine has a vacuum leak B. Reading shows normal wear C. Piston rings are worn D. Fuel injector is leaking
C. Piston rings are worn A bad valve, valve seals or worn piston rings results in oil burning in combustion chamber and black carbon deposits on the spark plug tip.
Any of these are true of cracked cap connecting rods EXCEPT: A. Any two rod and cap mating surfaces are different from all other B. They increase bearing cap mating strength C. Rods and caps should be marked by stamping D. Installing a cap in reverse orientation will damage the rod and cap
C. Rods and caps should be marked by stamping
Vacuum test performed on an engine with rough idle. Needle on gauge fluctuates between 15 in. Hg and 20 in. Hg vacuum at idle. Reading indicates: A. Late ignition or valve timing B. Normal condition C. Sticking valve or misfire D. Restricted exhaust system
C. Sticking valve or misfire A gauge that fluctuates between 15 in. Hg and 20 in. Hg indicates stuck valve or engine misfire.
An engine's turbocharger is producing too much boost. Which of the following is MOST likely causing this condition? A. A stuck open wastegate B. An intake manifold vacuum leak C. A stuck closed wastegate D. None of the above
C. Stuck closed wastegate - Boost sensor indicates overboost condition. A stuck closed wastegate, faulty control valve solenoid or line all results in an overboost condition. W/O this necessary reduction in output, excessive manifold and cylinder pressures could damage vital engine components.
Two technicians are discussing a PCV system. Tech A says a stuck closed PCV valve could cause external oil leaks. Tech B says that the PCV system removes blowby gases from the engine case. Who is correct? A. Tech A B. Tech B C. Tech A and B D. Neither A or B
C. Tech A and B - PCV (Positive Crankcase Ventilation) system removes piston blowby from the crankcase. The valve relies on controlled flow to route these fumes into the intake manifold for combustion. Stucked closed PCV valve results in excessive crankcase pressure and oil forced past seals and gaskets.
Two technicians discussing engine sealants and form in place of gaskets. Tech A says sealants such as RTV are aerobic. Tech B says some sensors may be damaged if an unapproved sealant is used. Who is correct? A. Tech A B. Tech B C. Tech A and Tech B D. Neither Tech A or B
C. Tech A and Tech B
Blue gray smoke comes from exhaust of a vehicle during deceleration. Which of the following is the LEAST likely cause? A. Worn valve guides B. Broken valve seals C. Worn piston rings D. Clogged oil return passages
C. Worn piston rings Worn piston rings will make engine smoke worse upon acceleration.
What must you check if the engine cranks slowly with an amperage and voltage over 11.5 volts?
Check the circuit for high resistance in the starter circuit. - Also inspect for damaged or corroded battery cables - Measure voltage drop between the starter and battery posts on both the power side and ground side of the starter circuit. Voltage should be 0.2 volts or less.
What must you check if the engine cranks slowly with an amperage above specification with voltage below 10 volts?
Check the engine for damage or a defective starter.
What are two methods to check main bearing oil clearance?
Checking by using a Plastigage or a dial bore gauge.
A vehicle vibrates only when placed in REVERSE. The MOST likely cause of this condition is: A. Crossed ignition vibration B. A faulty fuel injector C. A faulty balance shaft D. A broken engine mount
D. A broken engine mount
A vehicle briefly blows blue and gray smoke from the tailpipe when it's first started in the morning. The MOST likely cause of this condition is a: A. Worn piston ring B. Lean fuel condition C. Leaking fuel injector D. Leaking valve seal
D. A leaking valve seal - oil enters combustion chamber causing the vehicle to emit blue-gray exhaust from tailpipe. Exhaust pipe is most apparent at start up after vehicle is sitting for a while. Since the oil is on top of the cylinder head has had time to seep into the chamber and you run the engine. The oil will clear out, blue-gray smoke may disappear or not so apparent until next start up.
Compression test shows one cylinder is too low. Leakage test on cylinder shows that there's excessive leakage. During test, air could be heard coming from the tailpipe. Which of the following could be cause? A. broken piston rings B. Bad head gasket C. bad exhaust gasket D. An exhaust valve not seating
D. Exhaust valve not seating If the exhaust valve does not seat correctly, air will leak from the combustion chamber by the way out to the tailpipe and make an audible sound.
During initial inspection the technician notices that there's a strong sulfur odor emitting from the vehicle's tailpipe. The customer states that the vehicle has been getting poor fuel mileage. The MOST likely cause of this condition is: A. A lean fuel condition B. Leaking head gasket C. Worn piston rings D. A rich fuel condition.
D. A rich fuel condition
All of the following statements could cause reduced performance from a turbocharger engine EXCEPT: A. Dirty air filter B. Restricted exhaust system C. Work turbocharger bearings D. Stuck closed wastegate
D. A stuck closed wastegate will cause overboost. Dirty air filter and a restricted exhaust will inhibit air flow through the turbocharger and reduce performance. Worn turbocharger shaft bearings could cause the rotating assembly to bind or drag and reduce performance.
In order to perform a proper compression test, all of the following conditions should be met EXCEPT: A. Throttle blades should be held wide open B. Battery should be fully charged C. Engine should be at operating temperature D. Only the spark plug for the cylinder to be tested should be removed
D. All of the spark plugs should be removed so the engine will engine will crank more easily.
After replacing the lower radiator hose and adding coolant, the engine continues to overheat. Which of the following is MOST likely causing this condition? A. A faulty water pump impeller B. A leaking head gasket C. A faulty fan motor relay D. An air pocket in the cooling system
D. An air pocket in the cooling system Air pockets form high in the cooling system, even after replacing a component that requires a drain and refill. During refill, engine may overheat because air rises to the top of the system and is more compressible than coolant.
Customer complaining vehicle's engine uses too much oil. No external leaks are found. This could be caused by a worn: A. Oil pressure regulator B. Oil pump C. Intake valve seat D. Intake valve seal
D. An intake valve seal Upon the intake stroke, piston is moving downward pulling oil past the valve seat.
Technician is using a scan tool to perform a cylinder balance test on V-6 engine that has stored DTCs such as "Cylinder #2 Misfire Detected" and "Cylinder #6 Misfire Detected." Cylinders #2 and #6 have no RPM drop during the test. Compression and cylinder leakage tests were performed and the results are show. Any of these could be cause EXCEPT: A. Open spark plug wires B. Leakage intake gasket C. Plugged fuel injectors D. Burned exhaust valves
D. Burned exhaust valves will results to misfire and will show a loss of compression.
On vehicle test drive, it's noted the oil pressure light illuminates at idle but goes out immediately with the slightest increase in RPM. Which of these could be the cause? A. A restricted oil pickup tube screen B. Restricted oil filter C. Excessively worn valve guides D. Excessively worn main bearings
D. Excessive worn main bearings Excessive main bearing clearances results to wear and will reduce oil pressure.
An engine diagnosed for a knocking noise that's heard when the engine is cold, but not heard at operating temperature. This could be caused by a: A. Work crankshaft thrust bearing B. Cracked flex plate C. Binding piston pin D. Loose piston fit
D. Loose piston fit Loose piston fit - undersize piston or oversize cylinder bore can cause "piston slap" (temporary noise diminishes, completely stops as engine temperature rises and components expand).
Tech A says retarded valve timing can cause high cylinder compression readings. Tech B says lean air/fuel mixture can cause high intake manifold vacuum reading. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
D. Neither A or B - Retarded valve timing can cause valves to open and close at the wrong time, thus reducing compression and manifold vacuum readings. - Lean air/fuel mixture can cause a low but steady manifold vacuum reading. Air or vacuum leaks can cause a lean condition with symptoms such as rough idle, hesitation, stalling or hard starting.
Tech A says umbrella valve seals are installed in their operating position during cylinder assembly. Tech B says positive valve seals are positioned by the valve. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
D. Neither A or B - Umbrella seals are installed by pushing the seal down on the valve stem until it touches the valve guide boss. It will be positioned correctly the first time the valve opens. - Positive seals are tapped into place on guide boss during assembly using a special installation tool and small mallet
Tech A is rebuilding an engine with a timing chain. Tech B says rebuilding an engine with a timing belt. Tech A says timing chain is stretched and must be replaced, however timing sprockets appear to be in good shape so they can be reused. Tech B says is replacing timing belt and that requires him to also replace timing sprockets. Who is right?
D. Neither A or B A new timing chain should ALWAYS be installed on new sprockets. Unless they're damaged, it's not usually not necessary to replace the sprockets when replacing a timing belt.
Tech A says thermostat controls maximum engine temperature. Tech B says if engine continuously runs hot, install a cooler thermostat. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
D. Neither A or B Thermostat's function allow to engine come to operating temperature quickly and then maintain minimum operating temperature. ONLY the correct heat range thermostat should be installed. If thermostat is good and engine runs hot, another problem exists.
After performing a cylinder pressure test on a four cylinder engine, the #1 cylinder is 30 psi below specifications and all the other cylinders have passed. The pressure in the #1 cylinder increased after injecting engine oil. Tech A says excessive carbon build up on the piston head has cause these test results. Tech B says these results indicate a faulty intake or exhaust valve. Who is correct? A. Tech A B. Tech B C. Both Tech A and B D. Neither Tech A or B
D. Neither Tech A or B - After injecting oil into the cylinder, compare the results between a wet and dry to find the part causing the issue. If pressure readings increase after injecting oil, the piston rings are worn.
A manifold vacuum test is performed on an engine in a shop located approx. 4000 ft. above sea level. With the engine at normal operating temperature, gauge reads steady 15 in. Hg at idle. Which of the following indicated by this vacuum reading? A. Late ignition timing B. Low compression C. Vacuum leak D. Normal operation
D. Normal operation If shop located at sea level, other others can be indicated by this vacuum reading. But remember, atmospheric pressure changes with elevation and vacuum readings must be adjusted. For every 1000 ft. above sea level, remove 1 in. Hg of vacuum. If we correct for elevation, we can see engine will produce 19 in. Hg vacuum at idle at sea level, which is the parameters for normal engine operation.
Tech says retainer clips on pistons with floating pins should be reused if they're not damaged. Tech B says after full floating pin bushing is pressed into the rod, piston and rod is reassembled. Who is right? A. Tech A B. Tech B C. Both A and B D. Neither A or B
D. On engines with full floating wrist pins, retainer clips at ends of the pin should be always be replaced with new ones. Full floating bushings that are worn are replaced by pressing them in. Then they are finish honed to provide the correct clearance.
All of the following are statements describing normal mechanical fan clutch operation EXCEPT: A. Fan clutch has viscous drag regardless of temperature B. Fan clutch varies fan speed according to engine temperature C. Fan clutch stops the fan speed from spinning within two seconds after turning off a hot engine D. Fan clutch varies fan speed according to engine speed
D. Properly operating fan clutch will change the speed of the fan according to engine temperature. When engine is cold, fan clutch does not turn fan very fast even when engine speed is increased. As engine warms up, fan clutch increases speed of the fan. If fan speed varies only according to engine speed, regardless of temperature, then fan clutch is probably seized and should be replaced.
What is camshaft duration?
Duration refers to "time" meaning how long the valve stays open and measured in degrees of crankshaft rotation. When out of specifications, the valve opens and closes at the wrong time. The results in a loss of engine performance.
What happens when the valve seals wear?
Excessive oil will leak past the seal into the combustion chamber which results to blue & gray smoke at start up.
Does a weak valve spring increase installed height? TRUE or FALSE
FALSE A weak valve spring will not increase installed height.
What's the indication if the vacuum gauge drops slowly at idle?
If the gauge drops slowly at idle that indicates a clogged or blocked exhaust.
What's a return style fuel system?
It has a vacuum operated fuel pressure regulator and a return line. At idle and low engine speeds, pressure regulator returns fuel fuel to the tank results in excessive emissions.
What happens if the valve seat is worn?
It may cause compression or leakage problems but it does not affect oil consumption.
What is camshaft lift?
Lift refers to "how far the camshaft's lobe lifts the valve off the valve seat and into the cylinder. If the valve doesn't open far enough into the cylinder, there's a restriction in the air/fuel charge resulting in poor engine performance. It can be measured with a dial indicator placed on the valve's tip or an outside micrometer.
What's the indication if the vacuum gauge reads a steady low vacuum?
Steady low vacuum indicates late valve or ignition timing, leaking manifold gasket, low compression, leaking carburetor or stuck throttle valve.
What is valve lift?
The distance the valves are opened.
What does black flakey soot indicate on a spark plug?
The electrode of the spark plug indicates a rich fuel condition. Note: If spark plug is wet. Spark plug could be wet by oil, fuel, or coolant. Dripping fuel injector results in a wet spark plug tip that smells like raw fuel.
What will happen if the oil pump pick up screen is restricted?
The oil pump pick up will cause the drop in oil pressure.
What does a light tan or light gray indicate on a spark plug?
The spark plug indicates a normal condition. Center of the electrode should be square and not rounded.
What does the valve seal do?
Valve seals controls amount of oil lubricating the valve stem?
What is valve overlap?
When the intake and exhaust valves remain open at the same time
