GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 Regal (China) 🢒 Engine 🢒 Engine Controls - 2.5L (LB8) and 3.0L (L46) 🢒 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 Intermittent Conditions before starting.
    •  Search for bulletins.

Fuel System
    • Inspect for low fuel pressure. Refer to Fuel System Pressure Test .
    •  Inspect 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 in DTC P0172 Fuel Trim System Rich .

Ignition System

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

Engine Cooling System

Inspect 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. Refer to Coolant Description in Engine Cooling.

Engine Mechanical
    • Excessive oil in combustion chamber--Leaking valve seals. Refer to Base Engine Misfire 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 instructions on 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
    • Inspect for proper EGR system operation. Refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient .
    • Inspect the transaxle range switch input with the vehicle in drive and the gear selector in drive or overdrive.
    • Inspect the TCC operation. The TCC applying too soon can cause the engine to spark knock. Refer to Torque Converter Diagnosis in Automatic Transaxle-4T65-E.
    •  If the 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.