GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC P42 Commercial Chassis 🢒 Engine 🢒 Engine Controls - 6.5L (L57) 🢒 Lack of Power, Sluggishness, or Sponginess

Lack of Power, Sluggishness, or Sponginess EFI

Checks

Action

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

Preliminary Checks
    • Refer to Symptoms .
    • Compare the vehicle with a similar unit. Make sure that the vehicle has an actual problem.
    • Remove the air filter.
    • Check for dirt, or for air ducts being plugged. Clean and replace if necessary.
    • Inspect the transmission shift pattern and the down shift operation.
    • Check the fuel quality. Refer to Contamination Testing .
    • Check the engine oil level and quality.

Fuel System Checks
    • Check the fuel supply to the injection pump and the fuel return from the injection pump. Refer to Fuel Supply System Check .
    • Check the fuel pump operation. Refer to Fuel Supply System Check .
    • Check for malfunctioning fuel injection nozzles. Refer to Injection Nozzle(s) Diagnosis .

Exhaust System Checks
    • Check the exhaust system for a possible restriction. Refer to Exhaust Systems.
    • Inspect the exhaust system for damaged or collapsed pipes.

Air Intake System Checks
    • Check for an air leakage or a restriction in the air inlet ducts or the intake manifold.
    • Check for a worn or a damaged turbo charger turbine wheel, shaft or compressor wheel.

Engine Mechanical Check

Check the engine for the following:

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

Additional Checks
    • Check the control module grounds for being clean, tight, and in their proper location. Refer to Engine Controls Component Location.
    • Check the torque Converter Clutch (TCC) operation.
    • Check the A/C operation. Refer to A/C Systems.

Lack of Power, Sluggishness, or Sponginess MFI

Checks

Action

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

Preliminary Checks
    • Refer to Symptoms .
    • Compare the vehicle with a similar unit. Make sure that the vehicle has an actual problem.
    • Remove the air filter.
    • Check for dirt, or for air ducts being plugged. Clean and replace if necessary.
    • Inspect the transmission shift pattern and the down shift operation.
    • Check the fuel quality. Refer to Contamination Testing .
    • Check the engine oil level and quality.

Fuel System Checks
    • Check the fuel supply to the injection pump and the fuel return from the injection pump. Refer to Fuel Supply System Check .
    • Check the fuel pump operation. Refer to Fuel Supply System Check .
    • Check for malfunctioning fuel injection nozzles. Refer to Injection Nozzle(s) Diagnosis .

Exhaust System Checks
    • Check the exhaust system for a possible restriction. Refer to Exhaust Systems.
    • Inspect the exhaust system for damaged or collapsed pipes.

Air Intake System Checks
    • Check for an air leakage or a restriction in the air inlet ducts or the intake manifold.
    • Check for a worn or a damaged turbo charger turbine wheel, shaft or compressor wheel.

Engine Mechanical Check

Check the engine for the following:

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

Additional Checks
    • Check the control module grounds for being clean, tight, and in their proper location. Refer to Engine Controls Component Location.
    • Check the torque Converter Clutch (TCC) operation.
    • Check the A/C operation. Refer to A/C Systems.