ASE4 General Engine Diagnosis 3

Question 1

A technician performs a relative compression test using a scan tool. Which data parameter is monitored?

Accepted Answer

Cranking RPM variation per cylinder

Answer

MAF sensor grams/second

Answer

O2 sensor switching speed

Answer

Injector pulse width

Question 2

Blue smoke from the exhaust under hard acceleration most likely indicates:

Accepted Answer

Worn piston rings allowing oil consumption

Answer

A rich fuel mixture

Answer

Leaking valve stem seals

Answer

A clogged PCV valve

Question 3

A vacuum gauge shows a reading that slowly drops and then rises at idle. This indicates:

Accepted Answer

A restricted exhaust system

Answer

A sticking EGR valve

Answer

Lean air/fuel mixture

Answer

Late ignition timing

Question 4

An engine produces a loud knock only when cold that disappears after warm-up. This is MOST likely:

Accepted Answer

Piston slap due to worn pistons

Answer

Rod bearing knock

Answer

Valve train tick

Answer

Detonation from low-octane fuel

Question 5

When diagnosing an oil consumption complaint, the FIRST step is to:

Accepted Answer

Check for external oil leaks and confirm actual consumption

Answer

Perform a cylinder leakage test

Answer

Replace valve stem seals immediately

Answer

Perform a wet compression test

Question 6

A steady vacuum reading of 17–21 in-Hg at idle is considered:

Accepted Answer

Normal for a healthy engine at sea level

Answer

Too low, indicating a vacuum leak

Answer

Too high, indicating over-advanced timing

Answer

Normal only for turbocharged engines