Detonation/Spark Knock - With PCM

DEFINITION
A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening.

PRELIMINARY CHECKS
- Refer to Important Preliminary Checks. Testing and Inspection
- Make sure the customer has an actual problem.

IMPORTANT: If scan tool readings are normal see On-Board Diagnostic System Check and there are no engine mechanical faults, fill fuel tank with a known good grade of gasoline that has a minimum octane rating of 87 to 89 and revaluate vehicle performance. Testing and Inspection
- Transmission Range (TR) pressure switch assembly operation.

COOLING SYSTEM
Check:
- For obvious over heating problems.
- Low engine coolant.
- Loose water pump belt.
- Restricted air flow to radiator, or restricted coolant flow.
- Faulty or incorrect thermostat.
- Correct coolant solution.

FUEL SYSTEM
Check:
- To determine if the condition is caused by a lean system, the vehicle should be driven at the speed of the complaint. Monitoring fuel trim will help identify the problem.
- Lean - Long term fuel trim greater than 150. Refer to DTC 44 Diagnostic Aids. Powertrain Controls - ECM/PCM

- Fuel pressure. Refer to Chart A-6 Fuel System Diagnosis. Related Tests, Information and Procedures
- For poor fuel quality and proper octane rating.

IGNITION SYSTEM
Check:
- Spark plugs for proper heat range and gap.
- Knock Sensor (KS) system operation.
- Ignition timing.

ENGINE MECHANICAL
Check:
- For carbon buildup. Remove carbon with top engine cleaner. Follow instructions on can.
- For incorrect basic engine parts such as cam, heads, pistons, etc.

ADDITIONAL CHECKS
Check:
- Proper operation of EGR valve.
- Proper operation of air intake system.
- For proper transmission shift points.
- Torque Converter Clutch (TCC) operation.
- Service Bulletins for PROM updates.
- Combustion chamber pressure by performing a compression test.