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.

PRELIMINARY CHECKS
^ Perform the careful visual/physical checks as described at start of "Symptoms".
^ Transaxle range switch. Be sure Tech 1 scan indicates correct range.

NOTICE: If Tech 1 scan tool readings are normal refer to "On-Board Diagnostic (OBD) System Check" Testing and Inspection
If there are no engine mechanical faults, fill fuel tank with a premium gasoline that has a minimum octane reading of 92 and revaluate vehicle performance.

^ CHECK: EGR system for not opening. Use CHART C-7.
^ CHECK: TCC operation, TCC applying too soon. Use CHART C-8.

ADDITIONAL CHECKS
^ CHECK: Service Bulletins.for updates.

IGNITION SYSTEM
^ CHECK: Spark plugs for proper heat range.
^ CHECK: Knock Sensor (KS) system for no retard, use CHART C-5. 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.

COOLING SYSTEM
^ Check for obvious overheating problems:

- Low engine coolant.
- Loose water pump belt.
- Restricted air flow to radiator, or restricted water flow through radiator.
- Inoperative electric cooling fan circuit, use CHART C-12.
- Correct coolant solution should be a 50/50 mix of GM #1052753 anti-freeze coolant (or equivalent) and water.

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 long term fuel trim will help identify problem.

Lean - Long term fuel trim above 150. Refer to "Diagnostic Aids" on facing page of Diagnostic Trouble Code (DTC) 44.

Rich - Long term fuel trim below 110. Refer to "Diagnostic Aids" on facing page of Diagnostic Trouble Code (DTC) 45.

^ CHECK: Fuel pressure, use CHART A-7. Related Tests, Information and Procedures