Why my car cuts off @ idel?

What is your question?

have a 1994 Olds Cutlass Supreme S 3.1 and I had it checked to see why it cuts off, so I thought I needed an air idle control valve. Took it to Firestone and even when they put on the NEW part, it was doing it worse, so they put in an idle sensor & that didn't fixed it either, but they did cleaned the throttle body. They told me that I have to go to the dealer to see what was causing it. but I didn't have to pay for it since they couldn't fix it. They told me that it could be an electrical issue, in which I had it checked the 1st time, thinking I had an alternator issue, but that and the starter and battery was ok. So what could cause it to cut off @ idle?The battery I do have is over 4 years old.Thanks

What makes this problem better or worse?

it willn't cut off while driving

How long has your 1994 Oldsmobile Cutlass Supreme had this problem?

over @ least 4-5 weeks