General Engine Diagnosis Flashcards
6 cards from real ASE4 practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 General Engine Diagnosis flashcards as text
A customer complains of a rough idle that disappears at higher RPMs. Which tool is BEST used to identify a misfiring cylinder?
Answer: Scan tool with misfire counters
A scan tool displaying misfire counters can identify which specific cylinder is misfiring under live conditions.
A cylinder power balance test shows that shorting cylinder #3 causes no RPM drop. This indicates:
Answer: That cylinder is not contributing to engine power
No RPM drop when a cylinder is disabled means that cylinder was already not contributing power, indicating a fault.
Low compression on two adjacent cylinders most likely indicates:
Answer: A blown head gasket between those cylinders
A blown head gasket between two adjacent cylinders allows compression to leak between them, causing both to read low.
When performing a cylinder leakage test, air is heard escaping from the throttle body. This indicates:
Answer: A leaking intake valve
Air escaping back through the throttle body during a leak-down test indicates a leaking intake valve on that cylinder.
An engine has good compression but produces blue smoke at startup that clears after a few minutes. The MOST likely cause is:
Answer: Leaking valve stem seals
Valve stem seals allow oil to seep into the combustion chamber when the engine sits, burning off as blue smoke at startup.
A technician connects a vacuum gauge and observes a steady low reading of 12 in-Hg at idle. This MOST likely indicates:
Answer: Late ignition timing
A steady but low vacuum reading at idle typically points to late ignition timing reducing combustion efficiency.