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 .
    • Compare the customer's 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 Functional Test in Automatic Transmission.

Fuel System Checks

    • Check for a restricted fuel filter, contaminated fuel, or improper fuel pressure. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Perform the fuel injector balance test. Refer to Fuel Injector Balance Test .

Exhaust System Checks

    • Check the exhaust system for a possible restriction. Refer to Restricted Exhaust System Check .
    • 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. Refer to EGR System Check.
    • Check the Torque Converter Clutch (TCC) operation. Refer to Functional Test in Automatic Transmission.
    • Check the A/C operation. Refer to Air Conditioning (A/C) Compressor Control Circuit Diagnosis .
    • Check the generator output voltage. Refer to Charging System Check 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.