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 vehicle with a similar unit. Ensure the vehicle has an actual problem.
    • Remove the air filter and check for dirt, or for air ducts being plugged or restricted. Replace as necessary.
    • Inspect for a proper transmission shift pattern and down shift operation.
    • Inspect the fuel quality. Refer to Fuel Specific Gravity Testing .
    • Inspect the engine oil level and quality.

Fuel System Checks

    • Check the fuel pressure to the fuel injection pump. The fuel pressure should stay above 10 PSI through all engine speeds and loads. If the pressure drops, a restriction exists in the fuel supply lines between the pump and the fuel tank.
    • Inspect the fuel injection pump operation.
    • Inspect for restricted or plugged fuel injectors.

Exhaust System Checks

    • Inspect the exhaust system for a possible restriction. Refer to Restricted Exhaust in Engine Exhaust.
    • Inspect the exhaust system for leaks.

Air Intake System Checks

    • Inspect for an air leak or restriction in the air inlet ducts or the intake manifold. Refer to DTC P0234 .
    • Inspect for an air leak or restriction in the charged air cooler.
    • Inspect for a worn or damaged turbo charger turbine wheel, shaft or compressor wheel.

Engine Mechanical Check

Inspect the engine for the following conditions:

    • Low compression
    • Improper valve timing
    • Improper or worn camshaft

Additional Checks

    • Inspect the control module grounds for being clean, tight, and in their proper location.
    • Inspect the torque converter clutch (TCC) operation.
    • Inspect the A/C operation. Refer to Symptoms - HVAC Systems - Manual in HVAC.
    • Inspect the generator output voltage. Repair if less than 9 volts or more than 16 volts.