GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2003 🢒 DeVille 🢒 Engine 🢒 Engine Electrical 🢒 Lack of Power, Sluggishness, or Sponginess

Inspection/Test

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

Fuel System
    • Test the fuel pressure. Refer to Fuel System Diagnosis .
    • Test the fuel injectors. Refer to the following:
    • Inspect for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Inspect the following that may cause the engine to run rich:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

    • Any water intrusion in the HO2S connector
    • Engine oil contaminated by fuel
    • An EVAP canister purge condition
    • Incorrect fuel pressure--Refer to Fuel System Diagnosis .
    • A leaking fuel pressure regulator
    • Inaccurate MAF sensor
    • Blockage on the inlet screen of the MAF sensor
    • Vacuum hoses for splits, kinks and proper connections
    • The air intake duct for being collapsed or restricted
    • The air filter for being dirty or restricted--Refer to Air Cleaner Element Replacement

Inspect the following that may cause the engine to run lean:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

    • Any water intrusion into the HO2S connector
    • An exhaust leak between the HO2S and the engine--Refer to Exhaust Leakage in Engine Exhaust.
    • Any vacuum leaks
    • Incorrect fuel pressure--Refer to Fuel System Diagnosis .
    • An inaccurate mass air flow (MAF) sensor
    • Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Vacuum hoses for splits, kinks and proper connections

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

Engine Mechanical
    • Inspect for excessive oil in the combustion chamber-leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical - 4.6L.
    • Inspect for low cylinder compression. Refer to Engine Compression Test in Engine Mechanical - 4.6L.
    • Inspect for incorrect basic engine parts. Inspect the following:
       - Camshafts
       - Cylinder heads
       - Pistons, etc.

Automatic Transaxle

Inspect 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
    • Inspect the exhaust system for possible restrictions. Refer to Restricted Exhaust .
    • Inspect for proper torque converter clutch (TCC) operation. Refer to Torque Converter Diagnosis in Automatic Transaxle - 4T80-E.
    • Inspect for conditions that cause the engine torque management system to reduce engine power.