Detonation/Spark Knock/Pings

Definition: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening. Sounds like popcorn popping.

PRELIMINARY CHECKS

^ Perform the careful visual/physical checks as described in DIAGNOSTIC NOTES.
^ Transmission range switch. Be sure scan indicates drive with gear selector in drive or overdrive.

IMPORTANT: If scan tool readings are normal and there are no engine mechanical faults, fill fuel tank with a known quality gasoline that has a minimum octane rating of 87 and re-evaluate vehicle performance.

^ CHECK: TCC operation, TCC applying too soon. Chart C-8A Torque Converter Clutch (TCC) Diagnosis

COOLING SYSTEM

^ Check for obvious overheating problems:
- Low engine coolant.
- Loose water pump belt.
- Restricted air flow to radiator, or restricted coolant flow.
- Inoperative electric cooling fan circuit, Testing and Inspection
- Correct coolant solution should be a 50/50 mix of GM #1052753 anti-freeze coolant (or equivalent) and water.

FUEL SYSTEM

IMPORTANT: To determine if the condition is caused by a rich or lean system, the vehicle should be driven at the speed of the complaint. Monitoring block learn will help identify problem.

^ CHECK: Fuel pressure.

IGNITION SYSTEM

^ CHECK: Spark plugs for proper heat range. Refer to "Owner's Manual."
^ CHECK: Knock sensor system for proper operation, Chart C-5 Knock Sensor (KS) System Check

ENGINE MECHANICAL

^ CHECK: For excessive oil in the combustion chamber.
- Valve oil seals for leaking.
^ CHECK: Combustion chambers for excessive carbon build up. Remove carbon with top engine cleaner and follow instructions on can.
^ CHECK: Combustion chamber pressure by performing a compression test.
^ CHECK: For incorrect basic engine parts such as cam, heads, pistons, etc.

ADDITIONAL CHECKS

^ CHECK: TCC operation, TCC applying too soon. Chart C-8A Torque Converter Clutch (TCC) Diagnosis
^ CHECK: For correct PROM. (See Technical Service Bulletins.)