ASE Engine Diagnostics 5

Question 1

Right after a timing belt replacement, the engine sets a camshaft/crankshaft position correlation code. What is the most likely cause?

Accepted Answer

Timing belt installed one or more teeth off

Answer

A correlation code after belt work usually means the cam and crank are out of time.

Question 2

During a power balance test, disabling cylinder 4 causes almost no rpm drop while the others drop about 100 rpm. What does this mean?

Accepted Answer

Cylinder 4 is contributing little power

Answer

A cylinder that already makes little power causes almost no rpm change when disabled.

Question 3

A spark plug has a white, blistered insulator tip. What does this indicate?

Accepted Answer

Overheating from a lean mixture or a plug heat range that is too hot

Answer

Blistered white insulators result from excessive combustion chamber temperatures.

Question 4

A spark plug is covered in wet, black, oily deposits. What is the most likely cause?

Accepted Answer

Oil entering the cylinder through worn rings or valve guides

Answer

Wet oily deposits mean engine oil is getting into the combustion chamber.

Question 5

An ECT sensor reports -40°F on a fully warm engine. Which symptom is most likely?

Accepted Answer

Rich running, poor fuel economy, and black smoke

Answer

The PCM thinks the engine is cold and adds extra fuel, causing a rich condition.

ASE - Automotive Service Excellence Certified Tech Practice Test