Detonation/Spark Knock

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

POSSIBLE CAUSE ACTION

Lean operating condition - Check computer controls, refer to COMPUTERS AND CONTROL SYSTEMS

Poor or contaminated fuel - Check for excessive alcohol content, Testing and Inspection
- Recommend higher grade fuel

Incorrect fuel pressure - Pinpoint Tests

Vacuum leak - Inspect vacuum hoses for proper routing and damaged lines

Air Induction - Check air cleaner duct and valve door not operating properly, IA4 - Air Cleaner Duct and Valve System Diagnosis
- Check for inoperative bimetal sensor, IA2 - Air Cleaner Temperature (BI-Metal) Sensor Diagnosis