GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1998 🢒 Skylark 🢒 Engine 🢒 Engine Controls - 2.4L 🢒 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 Symptoms .
    • Search for service bulletins.

Fuel System
    • Check for low fuel pressure. Refer to Fuel System Diagnosis .
    •  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 DTC P0171 Fuel Trim System Lean .

Ignition System
    • Check the spark plugs for proper heat range and reach. Refer to Spark Plug Visual Diagnosis in Engine Electrical.
    • Check the knock sensor (KS) system for no retard timing.

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.
    • Correct coolant solution should be a 50/50 mix of GM 1052753 or equivalent antifreeze coolant and water. Refer to Coolant Concentration Testing in Engine Cooling.

Engine Mechanical
    • Excessive oil in combustion chamber-Leaking valve seals. Refer to Oil Leak Diagnosis in Engine Mechanical.
    • Low cylinder compression. Refer to Engine Compression Test in Engine Mechanical.
    • 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 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 Clutch Evaluation and Diagnosis in Automatic Transaxle.
    • If scan tool readings are normal and there are no engine mechanical malfunctions, fill the fuel tank with a known quality gasoline that has a minimum octane reading of 87 and re-evaluate vehicle performance.