GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2004 🢒 Regal 🢒 Engine 🢒 Engine Controls - 3.8L (L36 and L67) 🢒 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.
    • Refer to Visual/Physical Checks.
    • Search for bulletins.

Fuel System
    • Test for low fuel pressure. Refer to Fuel System Diagnosis .
    •  Test for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect 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 .

Ignition System

Inspect the spark plugs for proper heat range and reach.

Engine Cooling System

Inspect for obvious overheating conditions:

    • Low engine coolant. Refer to Loss of Coolant in Engine Cooling.
    • Restricted air flow to radiator, or restricted water flow through radiator
    • Inoperative electric cooling fan circuits. Refer to Cooling Fan Inoperative in Engine Cooling.
    •  Correct coolant solution. Refer to Cooling System Draining and Filling in Engine Cooling.

Engine Mechanical
    • Excessive oil in combustion chamber--Leaking valve seals--Refer to Oil Consumption Diagnosis in Engine Mechanical 3.8L.
    • Low cylinder compression--Refer to Engine Compression Test in Engine Mechanical 3.8L.
    • Combustion chambers for excessive carbon buildup--Clean using top engine cleaner. Follow instructions on can.
    • For incorrect basic engine parts--Inspect the following:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.

Additional Checks
    • Test for proper exhaust gas recirculation (EGR) system operation. Refer to DTC P0401 .
    • Inspect the Transaxle Range Switch input with the vehicle in drive and the gear selector in drive or overdrive.
    • Test torque converter clutch (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.