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ASE Automobile & Light Truck (A1–A8) — Practice Exam

A1 General engine diagnosis: practice questions

Our ASE A1–A8 bank has 20 questions on this topic. Here are 5 of them with answers; the full mock exam draws from every topic, like the real one.

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Question 1 · A1 Engine Repair

During a cylinder leakage test, air is heard escaping from the tailpipe. Where is the leak?

  1. Past the piston rings
  2. Past an intake valve
  3. Through the head gasket into the coolant
  4. Past an exhaust valve
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D. Past an exhaust valve — Air at the throttle body or intake means an intake valve; at the oil fill, the rings.

Question 2 · A1 Engine Repair

How can a technician tell a rod knock from a main bearing knock?

  1. A rod knock usually changes when that cylinder's spark is disabled
  2. A main knock always stops completely when that cylinder's fuel injector is disabled
  3. A rod knock is heard only at idle
  4. A main knock only occurs in cold weather
Show the answer

A. A rod knock usually changes when that cylinder's spark is disabled — Disabling the cylinder unloads that rod bearing.

Question 3 · A1 Engine Repair

A cylinder reads low on a dry compression test but rises noticeably after a little oil is added. What does this indicate?

  1. A burned exhaust valve that seals only when cold
  2. A leaking intake valve
  3. Worn or stuck piston rings
  4. A cracked cylinder head
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C. Worn or stuck piston rings — Oil temporarily seals the rings; valve leaks don't improve with the wet test.

Question 4 · A1 Engine Repair

What is the purpose of the PCV system?

  1. To vent fuel tank vapors to the air when the tank pressure is high
  2. To raise oil pressure at idle
  3. To draw crankcase vapors into the intake to be burned
  4. To cool the engine oil
Show the answer

C. To draw crankcase vapors into the intake to be burned — A stuck PCV valve can cause oil leaks, sludge or a rough idle.

Question 5 · A1 Engine Repair

A light, rapid ticking at half crankshaft speed that is loudest at the valve cover usually comes from what?

  1. Piston slap
  2. A worn main bearing, heard loudest at the oil pan rail
  3. The valve train, such as a collapsed lifter or excess lash
  4. A loose flywheel
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C. The valve train, such as a collapsed lifter or excess lash — Valve-train noise occurs at camshaft speed, half of crankshaft speed.

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