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."
^ Park/Neutral Position (PNP) switch. Make sure Tech 1 scan tool indicates drive with gear selector in drive or overdrive. Use CHART C-1A (if equipped). Chart C-1A Park/Neutral Switch Diagnosis
^ If Tech 1 scan tool readings are normal (see "On-Board Diagnostic (OBD) 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 re-evaluate vehicle performance.

^ CHECK: For Service Bulletins updates
^ CHECK: For correct EPROM. (See Service Bulletins.)

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. Chart C-12 Coolant Fan Control Circuit
- Correct coolant solution should be a 50/50 mix of GM #1052753 anti-freeze coolant or equivalent and water.

IGNITION SYSTEM

^ 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 leaks.
^ 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.
^ CHECK: Spark plugs for correct heat range and proper torque.

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 near 198. Refer to "Diagnostic Aids" of DTC 44 chart. Powertrain Controls - ECM/PCM
Rich - Long term fuel trim near 58. Refer to "Diagnostic Aids" of DTC 45 chart. Powertrain Controls - ECM/PCM

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

ADDITIONAL CHECKS

^ CHECK: EGR system - Use CHART C-7. Chart C-7 EGR System Check
^ CHECK: TCC operation, TCC applying too soon. Use CHART C-8. Chart C-8A Torque Converter Clutch (TCC) Diagnosis
^ CHECK: For intake valve deposits.