GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1997 🢒 Venture Ext. 🢒 Engine 🢒 Engine Controls - 3.4L (LA1) 🢒 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
    • Check for low fuel pressure. Refer to Fuel System Pressure Test .
    •  Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Test .
    •  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 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 circuit(s). Refer to Electric Cooling Fan Diagnosis .
    •  Correct coolant solution should be a 50/50 mix of GM 1052753 or equivalent antifreeze coolant and water. Refer to Engine Cooling.

Engine Mechanical
    • Excessive oil in combustion chamber-Leaking valve seals. Refer to Engine Mechanical.
    • Low cylinder compression. Refer to 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 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 in Transaxle Diagnosis.
    •  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.