GM Service Manual Online
For 1990-2009 cars only

Checks

Action

Definition: White, black, gray or blue smoke under load, idle or start up hot or cold.

Preliminary Check

    â€¢ Refer to Important Preliminary Checks.
    â€¢ Make sure the customer has an actual problem.
    â€¢ Check fuel quality. Refer to Specific Gravity Check in Fuel Systems.

Fuel System Checks

    â€¢ Injection pump. Refer to Fuel System Diagnosis in Fuel Systems.
    â€¢ Check the injection pump timing. Refer to Fuel Systems.
    â€¢ Check the injection nozzles. Refer to Fuel Systems.

Sensor Check

    â€¢ Check the Engine Coolant Temperature (ECT) sensor using the scan tool to compare the engine coolant temperature with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5° greater or less than the ambient air temperature on a cold engine, check for a high resistance in the coolant sensor circuit or the sensor itself.
    â€¢ Check the glow plug system operation.

Air Intake System Check

    â€¢ Check the air cleaner and air intake ducts for restriction.
    â€¢ Check for a restriction in turbo charger inlet duct.
    â€¢ Check for a restriction in intake manifold.

Engine Mechanical Check

    â€¢ Check for incorrect basic engine parts such as cam, heads, pistons, Etc.
    â€¢ Check for excessive oil entering combustion chamber.