what is pinging and how can you tell if your car is doing it.

 

sounds like marbles in a can sort of, you can hear it, at a low speed or going up a hill, put it in 4th and lug the engine, that is when you'll most likely hear it

 

pinging happens when your cars timing is too far advanced. you can tell when you are on full throttle and you can hear the valves "pinging". i normally do a test run and find the spot where the pinging stops. you do this by retarding the timing by turning the distibutor counter clockwise slightly. if you have a timing light it should be 14-12 degrees

 

Here ya go, google is a wonderful thing
http://en.wikipedia.org/wiki/Engine_knocking