what exactly is pinging...

[Mr 5 0]

Well, I'm tempted to say that you'll know it when you hear it as it's not a sound you would normally hear from your engine.

It should be most noticable when accelerating, especially under a load (up a hill - or in fifth gear at less than 45 mph).

Sounds like a rattle - a bit like a diesel engine - although it may be faint so you need to test for pinging (detonation) on a quiet road, no radio on, windows open.

Causes are many including failing EGR, running too hot, wrong plugs, too much timing and so on. The results from long-term or severe detonation are not good. If you have detonation you need to find the cause and do whatever it takes to fix the problem and eliminate the pinging, ASAP.