Chrysler Repair: hi again i nodust when..., fuel air mixture, combustion chamber

Question
  hi again  i nodust when i take off from a stop
  i can hear a noise that it sound like a chain noise that is comeing from under neth car but i don't no what it is i no a lot of people that have the same noise can you tell me what it is i sound like it ownly happenns when the engine get realy hot if i put it in park and reve gas i don't hear it thank you tim

Answer
Hi Tim,
If the noise is heard only when you are accelerating and disappears when you let up on the pedal, then I suspect it is a "ping" or pre-ignition of the fuel air mixture in the combustion chamber before the actual spark occurs. This happens because of hot spots in the chamber usually from the carbon built up on the walls which get very hot and burn the mixture before the spark would have done it. Other than opening up the engine and cleaning it out the most direct way to reduce or eliminate the "ping" is to buy one grade higher gasoline which has a higher octane rating. As long as the ping is only happening under heavy acceleration it probably won't do any damage to the engine, but if it pinged all the time that can be damaging. You can also reduce it by not pressing too hard on the pedal to speed up rapidly when you don't have to. That will save gas too.
Roland