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

A relative compression test measures the variation in cranking RPM as each cylinder comes up on compression stroke.

Question 2

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

Accepted Answer

Worn piston rings allowing oil consumption

Answer

Blue smoke under acceleration is caused by worn rings that allow oil to be drawn into the combustion chamber under high vacuum.

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 vacuum reading that gradually drops then rises indicates a restricted exhaust is causing backpressure to build and release.

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

Piston slap is common when pistons are cold and contracted, creating excess clearance in the bore that diminishes as the engine warms.

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

External oil leaks must be ruled out first before assuming internal consumption is the cause of low oil level.

ASE4 - ASE Automobile Engine Performance Practice Test