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 Preliminary Checks.
^ Transaxle range switch 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. Testing and Inspection

^ Check Torque Converter Clutch (TCC) operation, TCC applying too soon. Use 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.
- 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. 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 L.T. fuel trim will help identify problem.

ENGINE MECHANICAL CHECKS
^ 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
^ TCC operation. TCC applying too soon. Refer to Chart C-8A.
^ Exhaust Gas Recirculation (EGR) system, refer to CHART C-7. Chart C-7 Exhaust Gas Recirculation (EGR) Flow Check
^ For correct PROM. See Service Bulletins.