idling level low

When I'm stopped at a light or in traffic, Idle goes low and engine just stops. As long as car is in motion, engine seems to be running fine. When the car is in park, rpm dips a little but does not shut off. Only when it's in drive and stopped, it shuts off. Is this a timing belt problem, or something bigger? The cae has over 80,000 miles on it.
Please help.

When was the last time you changed/cleaned your air filter? I had the same prob, hten I replaced the filter, and no more problem.

it could be ur charging system...have some1 check ur battery,alternator,belts... do you have a system is ur car that might be the problem too, ur battery can't handle ur audio system.