Detonation/Spark Knock

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

POSSIBLE CAUSES
Ignition Systems
- Spark plug heat range.
- Ignition timing.
- Distributor cap (if applicable) arcing or carbon tracking inside cap.

Fuel Systems
- Fuel system pressure.
- Poor fuel quality, proper octane rating.

Emission Controls
- EGR valve not opening.

Engine Mechanical
- Incorrect basic engine parts such as cam, heads, pistons, etc.
- Excessive oil entering combustion chamber.
- Carbon build-up on pistons or combustion chamber.
- Engine overheating.