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 for obvious overheating problems. Normal range is 85°C-100°C (185°F-215°F).
- Low coolant.
- Loose water pump belt.
- Restricted air flow to radiator, or restricted water flow through radiator.
- Faulty or incorrect thermostat.
- Correct coolant solution - should be a 50/50 mix of anti-freeze/coolant and water.

CHECK:
- 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. Remove carbon with top engine cleaner. Follow instructions on can.