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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1999 🢒 Firebird 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Detonation/Spark Knock

Detonation/Spark Knock

Checks

Action

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

Preliminary Checks
    • Refer to Important Preliminary Checks 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 .
    • If the scan tool readings are normal (refer to supporting text of the Powertrain On-Board Diagnostic (OBD) System Check) and there are no engine mechanical faults, fill the fuel tank with a known high quality fuel that meets the vehicle's minimum octane requirements. Refer to Fuel System Specifications . Road test the vehicle and re-evaluate the vehicle's performance.

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Test for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Test for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect the items that can cause an engine to run lean (long term fuel trim near 24%). 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 .

Ignition System

Inspect the spark plugs for the proper heat range. Refer to Spark Plug Usage in Engine Electrical.

Engine Cooling System

Inspect for obvious overheating conditions:

    • Low engine coolant. Refer to Cooling System Draining and Filling and Coolant Concentration Testing in Engine Cooling for the type and amount of engine coolant to be used.
    • Restricted air flow to the radiator or restricted coolant flow through the radiator. Refer to Radiator Cleaning in Engine Cooling.
    • Inoperative electric cooling fan. Refer to Electric Cooling Fan Diagnosis .

Engine Mechanical

Inspect for the following engine mechanical conditions:

    • Excessive oil in combustion chamber-Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical-5.7L.
    • Low cylinder compression. Refer to Engine Compression Test in Engine Mechanical-5.7L.
    • Combustion chambers for excessive carbon buildup. Clean the combustion chamber by using top engine cleaner. Follow the instructions on the can.
    • Inspect for incorrect basic engine parts. Inspect the following:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.

Refer to Engine Mechanical-5.7L.

Additional Checks
    • Test the Park/Neutral Position (PNP) switch operation. Refer to Park/Neutral Position Switch Diagnosis .
    • Test the Transmission Torque Converter Clutch (TCC) operation. A TCC applying too soon can cause the engine to spark knock. Refer to Functional Test in Automatic Transmission 4L60-E.