Sample ASE4 - ASE Automobile Engine Performance Practice Questions

Try these questions from our free ASE4 - ASE Automobile Engine Performance practice tests. The correct answer and an explanation follow each question.

1. An engine has a wet compression test reading significantly higher than the dry test. This indicates:

   • A. A blown head gasket
   • B. Worn or damaged piston rings
   • C. Leaking intake valves
   • D. A cracked cylinder head

   Answer: B. Worn or damaged piston rings

   Adding oil temporarily seals worn rings, causing a wet reading much higher than the dry reading.

2. When performing a cylinder leakage test, air is heard escaping from the throttle body. This indicates:

   • A. A leaking exhaust valve
   • B. A leaking intake valve
   • C. Worn piston rings
   • D. A cracked piston

   Answer: B. A leaking intake valve

   Air escaping back through the throttle body during a leak-down test indicates a leaking intake valve on that cylinder.

3. A fuel pressure test shows correct pressure at idle but drops significantly under full throttle acceleration. This indicates:

   • A. A restricted fuel filter or weak fuel pump
   • B. A leaking fuel pressure regulator
   • C. A faulty MAP sensor
   • D. Stuck-open fuel injectors

   Answer: A. A restricted fuel filter or weak fuel pump

   Fuel pressure that drops under high-demand acceleration indicates the pump or filter cannot maintain adequate flow.

4. A technician performs a fuel injector balance test. One injector causes a smaller pressure drop than the others. This means that injector is:

   • A. Flowing too much fuel (stuck open)
   • B. Flowing too little fuel (clogged or weak)
   • C. Working normally
   • D. Leaking when the engine is off

   Answer: B. Flowing too little fuel (clogged or weak)

   A smaller pressure drop during an injector balance test means the injector delivered less fuel, indicating a restriction or weak coil.

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