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 COMPUTERIZED ENGINE CONTROLS

Poor or contaminated fuel Check for excessive alcohol content
Recommend higher grade fuel

Incorrect fuel pressure Proceed to FUEL PRESSURE TEST

Vacuum leak Inspect vacuum hoses for
proper routing and damaged lines
Check intake manifold and carb./throttle body base