GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Corvette 🢒 Engine 🢒 Engine Controls - 5.7L 🢒 Lack of Power, Sluggishness, or Sponginess

Lack of Power, Sluggish or Spongy

Checks

Action

DEFINITION: The engine delivers less than expected power. Little or no increase in speed when the accelerator pedal is pushed down part way.

Preliminary Inspections
    • Refer to Important Preliminary Inspections Before Starting in Symptoms .
    • Search for bulletins.
    • Inspect the PCM grounds for being clean, tight and in the proper locations. Refer to Engine Controls Schematics .
    • Remove the air filter element and inspect for dirt or for being restricted. Refer to Air Cleaner Element Replacement and replace as necessary.

Fuel System
    • Inspect both injector fuses for being open. An open injector fuse causes four ignition coils and four injectors not to operate. Replace the fuse. Inspect the ignition coil circuits and the injector circuits for an intermittent short to ground.
    • Test for proper fuel pressure. Refer to Fuel System Diagnosis .
    • Test for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect the items which can cause an engine to run rich (long term fuel trim near -13%). For a rich condition, refer to DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1 and DTC P0152 HO2S Circuit High Voltage Bank 2 Sensor 1 .
    • Inspect the items that can cause an engine to run lean (long term fuel trim near 23%). For a lean condition, refer to DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 and DTC P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1 .

Sensor/System
    • Test the operation of the Column Lock System. Refer to Diagnostic System Check - Body Control System in Body Control System.
    • Use a scan tool in order to monitor the KS system for excessive spark retard activity. Refer to Knock Sensor (KS) System Description .
    • An Extended Travel Brake Switch that is mis-adjusted or an Extended Travel Brake circuit that is open causes a perceived misfire under heavy load conditions from a stop. Use a scan tool in order to monitor the Extended Travel Brake Switch parameter. If the scan tool displays Extended Travel Brake Switch applied when the brake pedal is released refer to DTC P1575 Extended Travel Brake Switch Circuit .

Ignition System
    • Inspect both injector fuses for being open. An open injector fuse causes four ignition coils and four injectors not to operate. Replace the fuse. Inspect the ignition coil circuit and the injector circuits for an intermittent short to ground.
    • Wet down the secondary ignition system with water from a spray bottle. Wetting the secondary ignition system may help locate damaged or deteriorated components. Look/listen for arcing or misfiring as water is applied.
    • Test for proper ignition voltage output with spark tester J 26792 .
    • Remove the spark plugs and inspect for the following conditions:
       - Correct heat range; refer to Spark Plug Usage in Engine Electrical.
       - Wet plugs; refer to Spark Plug Visual Diagnosis in Engine Electrical.
       - Cracks; refer to Spark Plug Visual Diagnosis in Engine Electrical.
       - Wear; refer to Spark Plug Visual Diagnosis in Engine Electrical.
       - Improper gap; refer to Spark Plug Replacement in Engine Electrical.
       - Burned electrodes; refer to Spark Plug Visual Diagnosis in Engine Electrical.
       - Heavy deposits; refer to Spark Plug Visual Diagnosis in Engine Electrical.
    • An improper spark plug gap will cause a driveability concern. Gap the spark plugs using a wire gauge gap tool (J 41319). Refer to Spark Plug Replacement in Engine Electrical.
    • Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant or oil fouled. Refer to DTC P0172 Fuel Trim System Rich Bank 1 or DTC P0175 Fuel Trim System Rich Bank 2 for diagnosis of the rich condition. Refer to Spark Plug Visual Diagnosis in Engine Electrical for diagnosis of coolant or oil fouled spark plugs.
    • Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .

Engine Mechanical
    • Ensure that the engine coolant temperature is not above 130°C (266°F). This condition causes the PCM to operate in Engine Coolant Over temperature-Fuel Disabled Mode. While in Engine Coolant Over temperature-Fuel Disabled Mode, the PCM will turn the fuel off to four cylinders at a time to keep engine temperatures from reaching damaging levels. The system perceives the Engine Coolant Over temperature-Fuel Disabled Mode as a lack of power, miss, or rough idle. If the vehicle operates in Engine Coolant Over temperature-Fuel Disabled Mode, refer to Engine Overheating in Engine Cooling.
    • Excessive oil in combustion chamber-Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical.
    • For incorrect basic engine parts. Inspect the following:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.

Refer to Engine Mechanical.

Additional Inspections
    • Inspect the exhaust system for possible restrictions. Perform for the following:
       - Inspect the exhaust system for physical damage. Refer to Exhaust System Inspection in Engine Exhaust.
       - Inspect the exhaust manifold for a collapsed inner wall. Refer to Exhaust System Inspection in Engine Exhaust.
       - Inspect the mufflers for heat distress or possible internal failure. Refer to Exhaust System Inspection in Engine Exhaust.
       - Inspect for possible plugged Three-Way catalytic converters by comparing exhaust system back pressure on each side of engine. Refer to Restricted Exhaust System Check or Restricted Exhaust in Engine Exhaust.
    • Test the Transmission Torque Converter Clutch (TCC) for proper operation. Refer to Functional Test in Automatic Transmission-4L60E.