Engine Knock and Ping

Your engine SHOULD NOT knock when under load, particularly accelerating or climbing a hill. A knock will sound like little hammer noise from deep inside the engine; it can be heard from the passenger compartment. It is actually the pressure waves of two separate flame fronts colliding inside the cylinder and rattling the inside components. This can be extremely damaging and should be corrected immediately, either through use of a higher octane gasoline or through mechanical repair.

Engine ping, a mild form of knock, will sound similar to, but not be as loud as, engine knock. Ping is caused by premature ignition of the fuel and is also called preignition. However, excessive pinging can lead to knocking which will ruin an engine. Run-on and upper cylinder noise are also signs of potentially incorrect octane rated gasoline (too low).

A small amount of knock is acceptable in a diesel engine. If knock persists in a gasoline engine though, try to eliminate it through use of a different gasoline. Experiment with different brands. Use the high quality, nationally advertised ones. Local or relatively unknown brands may not actually have the octane rating advertised. If switching brands does not eliminate the engine knock, try gasoline with an octane rating of 2 or 3 points higher than your owner's manual recommends. If the higher octane gasoline does not work, mechanical repairs will be necessary.

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