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 in Diagnosis By Symptom/Preliminary Checks.Testing and Inspection

^ Transaxle range switch Park Reverse Neutral Drive Low (PRNDL) inputs. Be sure scan indicates drive with gear selector in drive or overdrive.

NOTICE:
If scan tool readings are normal (refer to Diagnostic System Check) and there are no engine mechanical faults, fill fuel tank with a premium gasoline that has a minimum octane rating of 92 and revaluate vehicle performance.

^ Check Torque Converter Clutch (TCC) operation, TCC applying too soon. Refer to Torque Converter Functional Check in System Diagnosis/Diagnostic Charts/C Charts/Chart C-8A. Chart C-8A Torque Converter Clutch (TCC) Functional Check


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, use Chart C-12 Coolant Fan Control Circuit in System Diagnosis/Diagnostic Charts/C Charts/Chart C-12. Chart C-12A Coolant Fan Functional Check

- Correct coolant solution should be a 50/50 mix of GM #1052753 anti-freeze coolant (or equivalent) and water.

FUEL SYSTEM
Check fuel pressure, use Chart A-7 Fuel System Diagnosis in System Diagnosis/Diagnostic Charts/A Charts/Chart A-7. Related Tests, Information and Procedures

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 (L.T.) fuel trim will help identify problem.

IGNITION SYSTEM
Check:
^ Spark plugs for proper heat range.
^ Knock sensor system for proper operation, use Chart C-5 Knock Sensor (KS) System Check in System Diagnosis/Diagnostic Charts/C Charts/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.
^ Combustion chambers for excessive carbon buildup. Remove carbon with top engine cleaner and follow instructions on can.
^ Combustion chamber pressure by performing a compression test.
^ For incorrect basic engine parts such as cam, heads, pistons, etc.

ADDITIONAL CHECKS
Check:
^ TCC operation. TCC applying too soon. Refer to Chart C-8A in System Diagnosis/Diagnostic Charts/C Charts/Chart C-8A. Chart C-8A Torque Converter Clutch (TCC) Functional Check

^ Exhaust Gas Recirculation (EGR) system, refer to Chart C-7 EGR System Check in System Diagnosis/Diagnostic Charts/C Charts/Chart C-7. Chart C-7 Exhaust Gas Recirculation (EGR) Flow Check

^ For correct PROM. See Service Bulletins.