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 customers vehicle with a similar unit. Verify the customer concern.
    • Remove the air filter and check for dirt or a restriction.
    • Inspect the transmission shift pattern and the downshift operation. Refer to Torque Converter Diagnosis in Automatic Transmission.

Fuel System Checks

    • Inspect 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

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

Additional Checks

    • Inspect the control module grounds for being clean, tight, and in their proper location.
    • Inspect the exhaust gas recirculation (EGR) valve for being open or partially open all the time. Refer to Exhaust Gas Recirculation (EGR) System Diagnosis .
    • Inspect the torque converter clutch (TCC) operation. Refer to Torque Converter Diagnosis in Automatic Transmission.
    • Inspect the A/C operation. Refer to Air Conditioning (A/C) Compressor Control Circuit Diagnosis .
    • Inspect the generator output voltage.
    • Inspect the knock sensor (KS) system.

Engine Mechanical Check

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

    • Engine compression
    • valve timing
    • Improper or worn camshaft.