GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2003 🢒 L300/LW300 🢒 Engine 🢒 Engine Controls - 3.0L (L81) 🢒 Detonation/Spark Knock

Inspection/Tests

Action

DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening.

Preliminary Inspections
    • Refer to Important Preliminary Inspections Before Beginning in Symptoms - Engine Controls .
    • Search for bulletins.
    • Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics .
    • If there are no engine mechanical faults, fill the fuel tank with a known high quality fuel that meets the vehicles minimum octane requirements. Road test the vehicle and re-evaluate the performance of the vehicle.

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool .
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect for the following conditions that may cause the engine to run lean:

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

       - Water intrusion in the heated oxygen sensor (HO2S) connector
       - An exhaust leak between the HO2S and the engine--Refer to Exhaust Leakage in Engine Exhaust.
       - Vacuum leaks
       - Incorrect fuel pressure--Refer to Fuel System Diagnosis .
       - Restricted fuel injectors--Refer to Fuel Injector Balance Test with Special Tool .
       - Fuel contamination--Refer to Accelerator Pedal Position Sensor Replacement .
       - Vacuum hoses that are split, kinked, or improperly connected

Sensor/System

Inspect for an engine coolant temperature (ECT) sensor that has shifted in value . Refer to Temperature Versus Resistance .

Ignition System
    • In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures:
       -  Spark Plug Inspection
       -  Spark Plug Replacement
    • Remove spark plugs and inspect for the following:
       - Correct heat range
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
       - Verify that the spark plugs are of the correct type.
    • Inspect for proper secondary ignition voltage output with J 26792 (SA9199Z) Spark Tester .
    • An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gauge gap tool.
    • If the spark plugs are found to be fouled, determine the cause before replacing the spark plugs.
    • Inspect for damaged or misaligned spark plug boots.
    • Inspect the ignition module for proper ground connection.

Engine Cooling System

Inspect for obvious overheating problems:

    • Low engine coolant--Refer to Loss of Coolant in Engine Cooling.
    • Faulty thermostat. Refer to Thermostat Diagnosis in Engine Cooling.
    • Restricted air flow to the radiator or restricted coolant flow through the radiator.
    • Inoperative electric cooling fan--Refer to Cooling Fan Inoperative in Engine Cooling.
    • Proper tension on the drive belts. Refer to Drive Belt Tensioner Diagnosis in Engine Mechanical.
    • Correct coolant solution should be a 50/50 mix. Refer to Cooling System Description and Operation in Engine Cooling

Engine Mechanical

Inspect for the following engine mechanical problems:

    • Excessive oil in combustion chamber--Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical.
    • High cylinder compression--Refer to Engine Compression Test in Engine Mechanical.
    • Combustion chambers for excessive carbon buildup--Clean the combustion chamber by using top engine cleaner. Follow the instructions on the can.
    • Incorrect camshaft timing
    • Inspect for incorrect, worn, or damaged basic engine parts. Inspect the following:
       - The camshaft
       - The cylinder heads--Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical.
       - The pistons, etc.--Refer to Piston, Connecting Rod, and Bearing Cleaning and Inspection in Engine Mechanical.
    • Refer to Symptoms - Engine Mechanical in Engine Mechanical.

Additional Inspections

Inspect the transmission torque converter clutch (TCC) operation. The TCC applying too soon can cause the engine to spark knock. Refer to Torque Converter Diagnosis in Automatic Transaxle - 4T40-E/4T45-E.