GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 DeVille 🢒 Engine 🢒 Engine Controls - 4.6L 🢒 Lack of Power, Sluggishness, or Sponginess

Checks

Action

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

Preliminary
    • Refer to Important Preliminary Checks Before Starting in Symptoms - Engine Controls .
    • Search for bulletins.

Sensor/System
    • Check the knock system (KS) for excessive spark retard.
    • Check the exhaust gas recirculation (EGR) system for proper operation.
    • Check for a dirty or damaged air cleaner element.
    • Check for collapsed, or damaged intake air ducting.

Fuel System
    • Check the fuel pressure. Refer to Fuel System Diagnosis .
    • Check the fuel injectors. Refer to the following:
    • Check for items that cause the engine to run rich, or lean.
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Ignition System
    • Check for proper connections at each ignition module assembly.
    • Check for proper ignition voltage output using the J 26792 Spark Tester.
    • Check the ignition coils for cracks or damage.
    • Check for a missing or damaged ignition module assembly grounding spring.
    • Check for damaged or misaligned spark plug boots.
    • Check the spark plugs. Refer to Spark Plug Inspection .

Engine Mechanical
    • Check for excessive oil in the combustion chamber-leaking valve seals.
    • Check for low cylinder compression. Refer to Engine Compression Test in Engine Mechanical.
    • Check for incorrect basic engine parts. Inspect the following:
       - Camshafts
       - Cylinder heads
       - Pistons, etc.

Automatic Transaxle

Check for proper operation of the transmission fluid pressure (TFP) manual valve switch. Refer to Harsh Garage Shift or Engine Hesitation on Acceleration in Automatic Transaxle 4T80-E.

Additional Checks
    • Check the exhaust system for possible restrictions.
    • Check for proper torque converter clutch (TCC) operation. Refer to Torque Converter Diagnosis in Automatic Transaxle.
    • Check for conditions that cause the engine torque management system to reduce engine power.