NAPA Engine Performance 4

Question 1

A hot engine pings during acceleration. Which sensor lets the PCM retard timing to stop it?

Accepted Answer

Knock sensor

Answer

The piezoelectric knock sensor detects detonation vibrations so the PCM can retard spark timing.

Question 2

An engine cranks but will not start, and the tachometer reads zero while cranking. Which sensor is the most likely failure?

Accepted Answer

Crankshaft position sensor

Answer

Without a crank position signal, the PCM sees no rpm and will not fire injectors or coils.

Question 3

When testing a coil-on-plug ignition coil, the most effective way to confirm a misfire follows the coil is what?

Accepted Answer

Swap the coil to another cylinder and see if the misfire moves

Answer

If the misfire code moves to the new cylinder with the coil, the coil is confirmed faulty.

Question 4

A spark plug with dry, black, sooty deposits most likely indicates what?

Accepted Answer

Rich mixture or weak spark

Answer

Dry carbon fouling is caused by a rich mixture, excessive idling, or weak ignition.

Question 5

A spark plug with blistered white insulator and melted electrodes indicates which condition?

Accepted Answer

Overheating from lean mixture or overadvanced timing

Answer

Blistering and melted electrodes indicate excessive combustion temperature, often from lean mixture, advanced timing, or wrong heat range.

NAPA - National Automotive Parts Association Certified Mechanic Practice Test