- Preliminary Diagnosis

There are four steps to diagnosing engine noise. You must determine the following conditions:
^ Type of noise.
^ Determine the exact operating condition under which the noise exists.
^ At what rate, and at what location in the engine.
^ Compare sounds in other engines to make sure you are not trying to correct a normal condition.

Identify the type of noise. For example, a light rattle or low rumble. Remember, engine noises are generally synchronized to either engine speed (caused by the crankshaft, connecting rods or pistons) or one-half engine speed (valve train noise). Try to determine the rate at which the noise is occurring.