I know it sounds like a simple question, but how can you be sure? I mean, I'm no engine expert so I don;t know what sounds are totally normal and what aren't. I've read some info on what causes it ie...low octane gas, and I also heard that once it happens, it can only get worse. Now is this entirely true and what exactly am I looking/listening for? Any and all comments are appreciated.

 

Pinging, also called engine knock, has a sound often described as an unpleasant irregular metallic rattle, similar to shaking a coffee can full of marbles. Pinging is pronounced when the engine is under load, such as climbing a hill or rapid acceleration.

Try one tankful of super-premium fuel. If the sound goes away, it was pinging.

Causes of pinging include:
- fuel AKI too low
- ignition timing too far advanced
- lean mixture
- carbon deposits in combustion chambers
- EGR valve stuck closed
- EGR passages obstructed with soot
- EGR vacuum signal hose(s) split, broken, or disconnected
- engine running too hot

There are other vehicle sounds which are similar to pinging. The most common example is an exhaust system heat shield which has become loose and rattles or buzzes, especially at certain engine RPMs.

Your Maxima has a Knock Sensor which detects pinging and signals the Engine Control Module (the computer). The ECM responds by retarding the ignition timing to eliminate the pinging. For this reason... IF your Knock Sensor is working... you have never heard your Maxima engine pinging.