GM Service Manual Online
For 1990-2009 cars only

Checks

Action

DEFINITION: The engine delivers less than expected power. There is little or no increase in speed when partially applying the accelerator pedal.

Preliminary Checks

    • Refer to Symptoms - Engine Controls .
    • Compare the customer vehicle with a similar unit. Verify the customer concern.
    • Remove the air filter and check for dirt or a restriction.
    • Check the transmission shift pattern and the downshift operation. Refer to Diagnostic Starting Point - Automatic Transmission in Automatic Transmission.

Fuel System Checks

    • Check for a restricted fuel filter, contaminated fuel, or improper fuel pressure. Refer to Fuel System Diagnosis .
    • Perform the fuel injector balance test. Refer to Fuel Injector Balance Test with Tech 2 .

Exhaust System Checks

    • Check the exhaust system for a possible restriction. Refer to Restricted Exhaust in Engine Exhaust.
    • Inspect the exhaust system for damaged or collapsed pipes. Inspect the muffler for heat distress or a possible internal failure.

Additional Checks

    • Check the control module grounds for being clean, tight, and in their proper location.
    • Check the EGR valve for being open or partially open all the time.
    • Check the torque converter clutch (TCC) operation. Refer to Diagnostic Starting Point - Automatic Transmission in Automatic Transmission.
    • Check the A/C operation. Refer to HVAC Compressor Clutch Does Not Engage and HVAC Compressor Clutch Does Not Disengage in HVAC.
    • Check the generator output voltage. Refer to Diagnostic System Check - Engine Electrical in Engine Electrical.
    • Check the knock sensor (KS) system.

Engine Mechanical Check

Check the engine for the proper operation of the following items:

    • Engine compression
    • Valve timing
    • Improper or worn camshaft