Detonation/Spark Knock

DEFINITION:

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

CHECK
- Engine overheating.
- For poor fuel quality, proper octane rating.
- Spark plugs for correct heat range.
- Ignition timing. See Vehicle Emission Control Information label.
- Distributor cap for arcing or carbon tracking inside cap.
- Fuel system for low pressure.
- Check EGR valve for not opening.
- For incorrect basic engine parts such as cam, heads, pistons, etc.
- Excessive oil entering combustion chamber.
- Carbon build-up on pistons or combustion chamber.
- Check turbo operation. (If applicable)