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 poping.

Preliminary Checks
^ Perform the visual/physical checks as described under Diagnostic Notes in this section.
^ Fill fuel tank with a premium gasoline that has a minimum octane rating of 92 and reevaluate vehicle performance.
^ CHECK: TCC operation, TCC applying too soon.

Cooling System
^ Check for obvious overheating problems:
- Low engine coolant.
- Restricted air flow to radiator, or restricted cool with flow through radiator.
- Inoperative coolant fan circuit.
- Correct coolant solution.

Fuel System

NOTICE: 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 O2S voltage will help identify problem.

Lean - Refer to "Diagnostic Aids" found in Diagnostic Trouble Code 25 under Computers and Control Systems/Procedures/Diagnostic Charts.

Rich - Refer to "Diagnostic Aids" found in Diagnostic Trouble Code 26 under Computers and Control Systems/Procedures/Diagnostic Charts.

^ CHECK: For poor fuel quality. proper octane rating.
^ CHECK: Fuel pressure.

Ignition System
^ CHECK: Spark plugs for proper heat range.
^ CHECK: Ignition timing. See "Vehicle Emission Control Information" label.

Engine Mechanical
^ CHECK: For excessive oil in the combustion chamber.
- Valve oil seals for leaking.
^ CHECK: Combustion chambers for excessive carbon buildup. Remove carbon with top engine cleaner and follow instructions on can.
^ CHECK: Combustion chamber pressure by performing a compression test.

Additional Checks
^ CHECK: For correct ECM/PCM calibration (See Technical Service Bulletins).
^ CHECK: Torque Converter Clutch (TCC) applying too soon.