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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2003 🢒 Grand Am 🢒 Engine 🢒 Engine Electrical 🢒 Detonation/Spark Knock

Detonation/Spark Knock

Inspection/Tests

Action

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

Preliminary Inspections
    • Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls .
    • Search for bulletins.
    • Inspect the powertrain control module (PCM) 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 vehicles performance.

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Sensor/System

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.

    • Any water intrusion in 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 .
    • Any restricted fuel injectors--Refer to Fuel System Diagnosis .
    • Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Any vacuum hoses that are split, kinked, or improperly connected

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 conditions:
       - 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 ignition voltage output with J 26792 HEI Spark Tester.
    • An improper spark plug gap will cause a driveability condition. Gap the spark plugs using a wire gage gap tool.
    • Determine the cause of the fouling before replacing the spark plugs.
    • Inspect for damaged or misaligned spark plug boots.
    • Inspect the electronic ignition (EI ) module for proper ground connection.

Engine Cooling System

Inspect for obvious overheating conditions:

    • Low engine coolant--Refer to Loss of Coolant in Engine Cooling .
    • A faulty thermostat--Refer to Thermostat Diagnosis in Engine Cooling.
    • A restricted air flow to the radiator or restricted coolant flow through the radiator
    • An 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 conditions:

    • Excessive oil in combustion chamber or 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 basic engine parts. Inspect the following components:
       - The camshaft--Refer to Camshaft Cleaning and Inspection in Engine Mechanical.
       - The cylinder heads--Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical.
       - The pistons, etc.--Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical.
    • Refer to Symptoms - Engine Mechanical in Engine Mechanical.

Additional Inspections
    • Inspect the park/neutral position (PNP) switch operation.
    • 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.