ASE A1 Engine Repair Practice Test

25 practice questions

Choose an answer, then check it under Show answer.

1. Question 1 of 25Easy

   An engine with normal oil change intervals has developed thick oil sludge deposits throughout the valvetrain. Inspection shows that the PCV valve pintle is seized completely shut. How does a seized-shut PCV valve cause engine oil sludge?

   1. AA. Crankcase oil pressure rises above the bypass valve opening pressure
   2. BB. Manifold vacuum siphons engine coolant across the cylinder head gasket
   3. CC. Trapped moisture and blow-by gases contaminate and degrade the engine oil
   4. DD. Excessive engine oil is drawn directly into the combustion chambers
   Show answer to question 1

   Answer: C. Trapped moisture and blow-by gases contaminate and degrade the engine oil

   The PCV system evacuates corrosive blow-by gases, unburned fuel vapors, and moisture from the crankcase. When the PCV valve is seized closed, these acidic vapors and moisture remain trapped inside the crankcase and mix with the engine oil, causing rapid chemical breakdown and severe sludge formation. A seized-shut PCV valve restricts vapor evacuation rather than pulling excessive liquid oil into the intake, and it does not affect oil pump gallery pressure.

2. Question 2 of 25Hard

   While finish-honing a cylinder bore, the technician notices that the crosshatch pattern is nearly horizontal, creating an included angle of only 15 degrees. Which of the following is the cause of this pattern?

   1. AA. The hone vertical stroking speed was too fast relative to drill rotation.
   2. BB. The hone vertical stroking speed was too slow relative to drill rotation.
   3. CC. Excessive honing oil was applied to the cylinder walls during operation.
   4. DD. The honing stone grit size was too coarse for the cylinder material.
   Show answer to question 2

   Answer: B. The hone vertical stroking speed was too slow relative to drill rotation.

   The typical recommended crosshatch included angle is 45 to 60 degrees. If the stroking speed up and down is too slow compared to the rotational speed of the hone, the lines become nearly horizontal (a flatter included angle). If the stroking speed is too fast relative to rotation, the crosshatch lines become too steep (nearly vertical).

3. Question 3 of 25Hard

   A mechanical gauge shows normal oil pressure at 2500 rpm but low pressure at hot idle. The oil level is correct and the oil is the viscosity specified by the manufacturer. Technician A says worn crankshaft and connecting rod bearings can lower hot idle pressure even when the oil pump is good. Technician B says oil pressure must be verified with a mechanical gauge at the specified rpm and oil temperature before the pump is condemned. Who is correct?

   1. AA. A only
   2. BB. B only
   3. CC. Both A and B
   4. DD. Neither A nor B
   Show answer to question 3

   Answer: C. Both A and B

   Excessive bearing clearance lets oil escape from the galleries faster than the pump can supply it, and the effect is greatest at hot idle when pump output is lowest. A mechanical gauge read at the manufacturer's specified speed and temperature is the accepted way to confirm actual pressure rather than trusting the dash gauge or sending unit. Both statements are true.

4. Question 4 of 25Easy

   A technician needs to determine whether the coolant in a vehicle provides adequate freeze protection for the local climate. Which test is MOST appropriate?

   1. AA. Pressure-test the radiator cap and compare release pressure with specification.
   2. BB. Check freeze point with a refractometer against the manufacturer's specification.
   3. CC. Measure voltage between coolant and ground with a voltmeter.
   4. DD. Use a pH strip to check acidity against a color chart.
   Show answer to question 4

   Answer: B. Check freeze point with a refractometer against the manufacturer's specification.

   Freeze protection depends on coolant concentration, and a refractometer or hydrometer measures that directly so it can be compared with the required protection. A cap pressure test checks the cap's ability to hold pressure, not the coolant's freeze point, while pH and voltage tests check other forms of coolant condition.

5. Question 5 of 25Medium

   A technician is preparing to locate a slow engine oil leak using fluorescent dye. Technician A says the dye must remain in the engine through at least 30 minutes of highway-speed driving before the ultraviolet light will reveal the leak. Technician B says the engine should be cleaned of old oil residue before the dye is added so the ultraviolet light shows only the fresh dye trail. Who is correct?

   1. AA. A only
   2. BB. B only
   3. CC. Both A and B
   4. DD. Neither A nor B
   Show answer to question 5

   Answer: B. B only

   The dye mixes with the oil almost immediately, so a short run at idle or a brief road test is enough to circulate it; extended highway driving is not required. Cleaning the engine first is essential, because old oil residue and some oil additives can fluoresce and create false trails that make the true source impossible to identify.

6. Question 6 of 25Medium

   An engine idles smoothly but misfires under load, and a spark tester connected to one coil output shows a steady spark at idle. Technician A says the tester gap can be opened wider to raise the voltage needed to fire and reveal a coil that is weak under demand. Technician B says a spark plug gap that has eroded wider over time raises the required firing voltage and can cause a misfire under load that does not occur at idle. Who is correct?

   1. AA. A only
   2. BB. B only
   3. CC. Both A and B
   4. DD. Neither A nor B
   Show answer to question 6

   Answer: C. Both A and B

   A wider tester gap demands more secondary voltage, which is how a coil that fires only at low demand is exposed as weak. An eroded plug gap also raises the voltage needed to fire the plug, and the higher cylinder pressure under load adds to that demand, so both technicians are correct.

7. Question 7 of 25Easy

   A vehicle has reduced power at highway speeds. The technician inspects the air intake system and finds the air filter element heavily loaded with dirt and debris. Which of these is the MOST likely effect of this restriction?

   1. AA. Reduced airflow into the engine at high demand
   2. BB. Unmetered air entering downstream of the throttle plate
   3. CC. Higher-than-normal intake manifold vacuum at idle
   4. DD. A lean fuel mixture at idle speed
   Show answer to question 7

   Answer: A. Reduced airflow into the engine at high demand

   A restricted air filter limits airflow most when demand is high, reducing maximum power. It does not create an unmetered air leak, and idle airflow is low enough that fuel trims are usually not affected.

8. Question 8 of 25Medium

   A customer says the engine has a dead spot when accelerating from a stop only when cold. Technician A says to verify the concern by starting the engine cold and recording throttle position, mass air flow and fuel trims during acceleration. Technician B says if the concern cannot be duplicated, check for pending codes and review freeze-frame data before returning the vehicle. Who is correct?

   1. AA. A only
   2. BB. B only
   3. CC. Both A and B
   4. DD. Neither A nor B
   Show answer to question 8

   Answer: C. Both A and B

   A cold-only driveability complaint must be reproduced from a cold start while the relevant scan data are recorded. If it cannot be duplicated, pending codes and freeze-frame data can still point to the conditions present when the fault was detected, so both technicians are correct.

9. Question 9 of 25Medium

   An engine cranks at normal speed but will not start. A vacuum gauge connected to an intake manifold port reads a steady 0 in. Hg during cranking. Which of these mechanical conditions is the MOST likely cause?

   1. AA. Excessive intake valve carbon deposits
   2. BB. Exhaust restriction from a plugged catalytic converter
   3. CC. Camshaft drive out of time due to a sheared drive pin
   4. DD. Leaking cylinder head gasket between two cylinders
   Show answer to question 9

   Answer: C. Camshaft drive out of time due to a sheared drive pin

   A normal cranking engine creates 3 to 5 in. Hg of fluctuating vacuum as pistons descend during intake strokes with functioning valve events. If camshaft drive timing is lost due to a sheared pin or gear, the valves do not open and close at the proper times to generate intake vacuum, resulting in a steady zero reading. A blown head gasket between cylinders produces an erratic or pulsating vacuum reading rather than zero.

10. Question 10 of 25Easy

    A technician is preparing to remove an engine assembly from a vehicle. Which of these should be done first?

    1. AA. Remove the radiator hoses.
    2. BB. Remove the hood.
    3. CC. Unbolt the engine mounts.
    4. DD. Disconnect the negative battery cable.
    Show answer to question 10

    Answer: D. Disconnect the negative battery cable.

    Disconnecting the negative battery cable first reduces the risk of electrical shorts or sparks while fuel and electrical components are being disconnected. Radiator hoses, mounts and the hood are removed later in the procedure.

11. Question 11 of 25Medium

    A port fuel-injected engine exhibits an extended crank after sitting turned off for 30 minutes, but restarts immediately if restarted right away. A fuel pressure gauge connected to the fuel rail shows that pressure drops to 0 psi within seconds of turning the ignition key off. Which of these is the LEAST likely cause of this rapid pressure drop?

    1. AA. A ruptured fuel pressure regulator diaphragm
    2. BB. A leaking fuel pump check valve
    3. CC. A leaking fuel injector
    4. DD. A restricted fuel pump inlet strainer
    Show answer to question 11

    Answer: D. A restricted fuel pump inlet strainer

    A restricted fuel pump inlet strainer reduces fuel volume and causes starvation at high engine speeds or heavy loads, but it does not cause residual fuel pressure to bleed off after key-off. A leaking check valve, a dripping fuel injector, or a ruptured regulator diaphragm all allow pressurized fuel to escape the fuel rail after shutdown.

12. Question 12 of 25Medium

    While replacing a leaking exhaust manifold gasket, a technician checks the manifold flange with a straightedge and finds it warped beyond the manufacturer's specification. Which is the correct action?

    1. AA. Over-torque the fasteners to pull the flange flat
    2. BB. Resurface or replace the manifold before installing the gasket
    3. CC. Apply sealant to the outside of the joint
    4. DD. Stack two gaskets to take up the gap at the flange
    Show answer to question 12

    Answer: B. Resurface or replace the manifold before installing the gasket

    A warped flange will not seal against a new gasket, so the mating surface must be restored by resurfacing or replacing the manifold. Stacking gaskets, over-torquing, or sealing the outside of the joint will not correct the gap and can crack the manifold or break studs.

13. Question 13 of 25Medium

    Both the primary and secondary resistance of a coil-on-plug coil measure within the manufacturer's specification, yet the engine misfires under load. Technician A says a coil can pass a resistance test and still break down under load. Technician B says a resistance measurement does not test the coil insulation at high voltage, so a loaded spark test may be needed. Who is correct?

    1. AA. A only
    2. BB. B only
    3. CC. Both A and B
    4. DD. Neither A nor B
    Show answer to question 13

    Answer: C. Both A and B

    An ohmmeter applies only a few volts, so a coil whose insulation breaks down at high firing voltage can still show correct resistance readings. Both statements describe that same limitation and the need for a high-voltage loaded test to expose the fault.

14. Question 14 of 25Medium

    An engine idles and then stalls when the technician wiggles the wiring harness near the PCM. Technician A says this confirms the PCM is defective and should be replaced. Technician B says the harness and connectors should be inspected for loose terminals, chafing, and poor grounds. Who is correct?

    1. AA. A only
    2. BB. B only
    3. CC. Both A and B
    4. DD. Neither A nor B
    Show answer to question 14

    Answer: B. B only

    Wiggling the harness changes the symptom, which points to an intermittent connection in the wiring or connectors rather than proof of a failed PCM. Inspecting and repairing the harness, terminals, and grounds is the correct next step; replacing the PCM first could leave the real fault in place.

15. Question 15 of 25Hard

    A vehicle overheats on the highway. A cooling system pressure test holds the specified pressure. With the engine at operating temperature, the upper radiator tank is hot while the lower tank and lower hose are cool, and the large temperature difference remains after the thermostat opens. Which of these is the MOST likely cause?

    1. AA. Restricted coolant flow through the radiator.
    2. BB. Cooling fan running continuously.
    3. CC. Radiator cap releasing below its rating.
    4. DD. Thermostat stuck open.
    Show answer to question 15

    Answer: A. Restricted coolant flow through the radiator.

    A large temperature difference between the hot upper tank and cool lower tank with a system that holds pressure indicates restricted flow through the radiator, so the radiator needs service or replacement. A cap releasing early would cause coolant loss and boil-over, while a stuck-open thermostat or continuously running fan would tend to run the engine too cool.

16. Question 16 of 25Medium

    A hollow rattling noise is heard from the engine for the first two to three minutes after a cold start. The noise fades as the engine warms and is not present at steady cruise. Which of these is the MOST likely cause?

    1. AA. A loose spark plug
    2. BB. Excessive piston-to-cylinder clearance
    3. CC. Excessive crankshaft end play
    4. DD. A worn camshaft lobe
    Show answer to question 16

    Answer: B. Excessive piston-to-cylinder clearance

    A hollow rattle present only while the engine is cold and fading as it warms is piston slap, caused by excessive piston-to-cylinder clearance that closes up as the pistons expand. Crankshaft end play knock is heard when torque loads the crankshaft fore and aft and does not fade with warm-up, and neither a worn camshaft lobe nor a loose spark plug produces this cold-only pattern.

17. Question 17 of 25Easy

    An engine suffered a severe connecting rod bearing failure that dispersed metal debris throughout the lubrication system. The engine is equipped with an external plate-style engine oil cooler. Technician A says the engine oil cooler must be replaced because trapped metal debris cannot be completely flushed from its passages. Technician B says reverse-flushing the oil cooler with solvent will reliably remove all embedded bearing material so the cooler can be reused. Who is correct?

    1. AA. A only
    2. BB. B only
    3. CC. Both A and B
    4. DD. Neither A nor B
    Show answer to question 17

    Answer: A. A only

    Technician A is correct because modern plate-style oil coolers contain tiny, intricate passages that easily trap metallic flakes and bearing debris; even high-pressure flushing cannot ensure complete removal, leading to debris re-entering the newly rebuilt engine and causing premature failure. Technician B is incorrect because reverse-flushing is not considered reliable for clearing bearing material from plate-style coolers, making cooler replacement mandatory.

18. Question 18 of 25Easy

    While performing a cylinder leakage test on cylinder 1, the gauge indicates 40% leakage. The technician hears air escaping from the tailpipe. Which of these is the MOST likely cause?

    1. AA. A burned exhaust valve
    2. BB. A restricted catalytic converter
    3. CC. A leaking cylinder head gasket
    4. DD. Worn valve stem seals
    Show answer to question 18

    Answer: A. A burned exhaust valve

    Air escaping from the tailpipe during a cylinder leakage test indicates that an exhaust valve is not seating properly due to burning, warping, or face damage. Leaking valve stem seals allow oil into the combustion chamber but do not seal cylinder pressure, and a restricted catalytic converter does not cause air to leak past a closed exhaust valve.

19. Question 19 of 25Hard

    A technician is rebuilding an engine equipped with a direct gear-to-gear camshaft drive. An audible clattering noise was previously heard from the front cover at idle. How should the technician measure camshaft gear backlash?

    1. AA. Measure the radial runout of the gear teeth using a dial indicator while rotating the crankshaft one full turn
    2. BB. Insert a flat feeler gauge between the rear face of the camshaft gear and the front of the thrust plate
    3. CC. Use a depth micrometer to measure the tooth contact depth at four equidistant points around the circumference
    4. DD. Mount a dial indicator on a tooth of the driven gear and rock the gear while holding the mating gear stationary
    Show answer to question 19

    Answer: D. Mount a dial indicator on a tooth of the driven gear and rock the gear while holding the mating gear stationary

    Gear backlash is the clearance between mating gear teeth and is properly measured by mounting a dial indicator perpendicular to a tooth on one gear, immobilizing the mating gear, and rocking the first gear back and forth to read total movement. Using a feeler gauge between the gear hub and thrust plate measures camshaft end play rather than backlash. Measuring radial runout checks gear concentricity, which does not directly measure tooth clearance.

20. Question 20 of 25Easy

    A technician uses Plastigage to check camshaft journal oil clearance on an aluminum overhead camshaft cylinder head. After torquing the bearing cap bolts to specification and removing the cap, the compressed Plastigage is wider than the minimum clearance mark on the scale. What does this measurement indicate?

    1. AA. Oil clearance is tighter than specification.
    2. BB. Camshaft journal end play is excessive.
    3. CC. Oil clearance is greater than specification.
    4. DD. The camshaft bearing journal is tapered.
    Show answer to question 20

    Answer: A. Oil clearance is tighter than specification.

    Plastigage flattens more as bearing clearance decreases; therefore, a wider compressed strip indicates that the oil clearance is tighter than the minimum specification. If clearance were excessive, the strip would be compressed less and appear narrower than the scale markings.

21. Question 21 of 25Medium

    An engine idles rough and has positive long-term fuel trims on both banks. A technician hears a hiss near the intake manifold and suspects an intake vacuum leak. Which test would BEST confirm the location?

    1. AA. Introduce smoke into the intake with a smoke machine
    2. BB. Measure fuel pressure with the key on
    3. CC. Pressure test the cooling system
    4. DD. Perform a cylinder compression test
    Show answer to question 21

    Answer: A. Introduce smoke into the intake with a smoke machine

    A smoke machine fills the intake with visible smoke and shows exactly where it escapes, making it the best test to locate an intake vacuum leak. A compression test checks cylinder sealing, a cooling system pressure test checks coolant leaks, and a key-on fuel pressure test does not locate a vacuum leak.

22. Question 22 of 25Medium

    A cooling system uses a bypass-blocking (dual-valve) thermostat. If the secondary bypass disc fails to close when the main valve opens, which symptom will MOST likely occur?

    1. AA. Excessive cabin heater temperature during engine idle
    2. BB. Prolonged engine warm-up time in cold ambient conditions
    3. CC. Coolant leakage around the thermostat housing mating surface
    4. DD. Engine overheating during highway or heavy-load driving
    Show answer to question 22

    Answer: D. Engine overheating during highway or heavy-load driving

    A bypass-blocking thermostat is designed to shut off the internal engine bypass circuit when the main valve opens to route coolant to the radiator. If the bypass disc fails to seat, hot coolant recirculates directly back into the engine instead of going through the radiator, leading to overheating under high-speed or heavy-load conditions. A thermostat stuck open causes prolonged warm-up, not a failed bypass disc.

23. Question 23 of 25Hard

    A technician is diagnosing excessive belt vibration on an engine equipped with an overrunning alternator pulley (OAP). Technician A says that an overrunning alternator pulley should freewheel smoothly when rotated in both directions by hand with the belt removed. Technician B says that a seized overrunning alternator pulley will cause the belt to slip continuously without affecting tensioner arm movement. Who is correct?

    1. AA. A only
    2. BB. B only
    3. CC. Both A and B
    4. DD. Neither A nor B
    Show answer to question 23

    Answer: D. Neither A nor B

    Both technicians are incorrect. Technician A is incorrect because an overrunning alternator pulley has an internal one-way clutch designed to lock in the driving direction and freewheel only in the opposite direction. Technician B is incorrect because when an overrunning pulley seizes solid, crankshaft torsional vibrations transmit directly into the belt drive, causing severe belt flutter and violent tensioner arm oscillation.

24. Question 24 of 25Hard

    A vehicle equipped with variable valve timing (VVT) sets a camshaft timing slow-response diagnostic trouble code (DTC) shortly after an oil change. The technician discovers that 20W-50 oil was installed instead of the specified 0W-20 oil. Which statement explains the MOST likely cause of the DTC?

    1. AA. The higher-viscosity oil restricts flow through small hydraulic passages to the phaser.
    2. BB. The higher-viscosity oil creates foam that collapses the hydraulic lifters.
    3. CC. The heavier oil forces the oil pump bypass valve open, cutting all oil pressure.
    4. DD. The heavier oil sticks the camshaft position sensor to the reluctor wheel.
    Show answer to question 24

    Answer: A. The higher-viscosity oil restricts flow through small hydraulic passages to the phaser.

    Modern variable valve timing phasers rely on precise hydraulic oil flow through small solenoid spool valves and galleys to advance and retard camshaft timing. Oil that is significantly more viscous than specified flows too slowly through these restricted orifices, resulting in delayed phaser movement and slow-response DTCs. Excessive oil viscosity does not collapse hydraulic lash adjusters or stop oil flow completely, though it delays hydraulic response.

25. Question 25 of 25Hard

    Before servicing an engine's accessory drive belt system on a mild-hybrid vehicle equipped with a 48-volt belt-alternator starter (BAS), which manufacturer service precaution must be observed?

    1. AA. Depressurize the mechanical fuel injection rail before touching the drive belt.
    2. BB. Short the auxiliary battery terminals using a fused jumper wire to drain residual capacitance.
    3. CC. Disconnect the variable valve timing solenoids to lock the camshaft phasers into base park timing.
    4. DD. Disable the 48-volt electrical system and verify zero energy before beginning mechanical work.
    Show answer to question 25

    Answer: D. Disable the 48-volt electrical system and verify zero energy before beginning mechanical work.

    A 48-volt mild-hybrid system utilizes a high-torque belt-alternator starter that can initiate an engine restart automatically at any time and carries higher-voltage shock and pinch hazards. Manufacturer precautions require powering down/disabling the 48-volt circuit (via disconnect plug, interlock, or service switch) and confirming zero voltage before working on the accessory drive belt. Shorting battery terminals with a jumper is dangerous and incorrect.

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