What causes car to stall after idling for 15 minutes?

Could be many reasons, so check obvious ones first, such as; worn spark plugs, vacuum leak - listen for hissing noises and check visually all hoses, idle speed to low- check AIC valve (try tapping on it, they often get stuck), Impurities in gas- add a fuel additive, Make sure gas cap is tight and correct one, If it only happens on damp days it could be bad wires op distributor cap-run at night and check for sparks with hood open.