GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Impala 🢒 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 in Symptoms before starting.
    • Refer to Visual/Physical Checks in Symptoms .
    • Search for bulletins.

Fuel System
    • Check for low fuel pressure. Refer to Fuel System Pressure Test (VIN K) .
    •  Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Check items that can cause an engine to run lean Long Term Fuel Trim significantly in the positive range. Refer to Diagnostic Aids for DTC P0171 Fuel Trim System Lean .

Ignition System

Check the spark plugs for proper heat range and reach. Refer to Maintenance Items in General Information.

Engine Cooling System

Check for obvious overheating problems:

    • Low engine coolant
    • Restricted air flow to radiator, or restricted water flow through radiator.
    • Inoperative electric cooling fan circuits. Refer to Electric Cooling Fan Diagnosis .
    •  Correct coolant solution should be a 50/50 mix of GM 1052753 or equivalent antifreeze coolant and water.

Engine Mechanical
    • Excessive oil in combustion chamber-Leaking valve seals.
    • Low cylinder compression.
    • Combustion chambers for excessive carbon buildup. Clean using Top engine cleaner. Follow instructions on can.
    • For incorrect basic engine parts inspect the following components:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.
    • Refer to Engine Compression Test in Engine Mechanical.

Additional Checks
    • Check for proper EGR system Operation. Refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient .
    • Check the transaxle range switch input with the vehicle in drive and the gear selector in drive or overdrive.
    • Check TCC operation. TCC applying too soon can cause the engine to spark knock. Refer to Torque Converter Diagnosis in Automatic Transaxle - 4T65-E.
    • If scan tool readings are normal and there are no engine mechanical faults, fill the fuel tank with a known quality gasoline that has a minimum octane reading of 87 and re-evaluate vehicle performance.