GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 LeSabre 🢒 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 .
    • Refer to Visual/Physical Check in Symptoms .
    • Search for bulletins.

Fuel System
    • Check the 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. Refer to DTC P0171 Fuel Trim System Lean .

Ignition System

Check the spark plugs for proper heat range. Refer to Maintenance Items .

Engine Cooling System

Check for obvious overheating problems:

    • Check for low engine coolant.
    • Check for a restricted air flow to the radiator or restricted water flow through the radiator.
    • Check the electric cooling fans' operation. Refer to Electric Cooling Fan Diagnosis .
    • Inspect for the correct coolant solution. A 50/50 mixture of ethylene glycol (Dexcool®) should be used. Refer to Coolant Concentration Testing .

Engine Mechanical
    • Inspect for excessive oil in combustion chamber or leaking valve seals. Refer to Oil Consumption Diagnosis .
    • Check for low cylinder compression. Refer to Engine Compression Test .
    • Check the combustion chambers for excessive carbon buildup. Clean using Top engine cleaner. Follow the instructions on the can.
    • For incorrect basic engine parts. Inspect the following:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.
    • Refer to Base Engine Misfire Diagnosis

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. Refer to Diagnostic Starting Point - Automatic Transmission .
    • Check the TCC operation. A malfunctioning TCC can cause the engine to spark knock. Refer to Diagnostic Starting Point - Automatic Transmission .
    • If scan tool readings are normal and there are no engine mechanical problems, fill the fuel tank with a known quality gasoline that has a minimum octane rating of 87 and re-evaluate the vehicle performance.