DIAGNOSE – ENGINE PINGS OR KNOCKS ON ACCELERATION

by Kyle McFadden

SYMPTOM SUMMARY
The engine “pings” or knocks on acceleration. The symptom is more pronounced when the engine is at operating temperature.

USUAL CAUSE
Engine ping is the result of abnormally high combustion temperatures. The usual cause of engine ping is over advanced ignition timing, an inoperative EGR system or improper fuel usage. A defect in the cooling system can also result in engine ping.

DIAGNOSIS
First, do not confuse engine ping with a mechanical failure that produces an internal knock in the engine. An engine knock will be a deep sound that eminates from the engines lower section and will be present under almost all operating conditions. Engine ping is usually present during moderate to heavy engine acceleration after the engine has reached or is near operating temperature. The ignition timing should be inspected and adjusted according to manufacturers specifications. Some vehicles use computer controlled ignition timing that is not adjustable. Consult your owners manual for the recommended fuel rating. A vehicle that is designed to operate on high octane fuel should not be operated using lower octane fuel. Switching to a higher octane fuel may be the only corrective action necessary. If the ignition timing and fuel octane rating are correct, a functional check of the EGR valve will be necessary. Inspect the vehicles cooling system operation. If the vehicle is running hotter than normal or overheating, than that symptom should be diagnosed first. Refer to the “Engine Overheats” article for further diagnosis.

PRECAUTIONS, TIPS, and NOTES
Use caution when working around hot or rotating engine parts.

(Kyle has an affinity for Pale Ale and tooling on his 1956 Chevrolet Nomad Station Wagon.)