general problems of the 1998 Oldsmobile Aurora

Car stalls once a day, almost every day in traffic. Sometimes it doesn't quite stall and catches itself and learches forward a few feet. Neither Oldsmobile or indipendent mechanics can find the problem. Tha codes are there in memory of the car but the codes do not say what to do about the problem. Know one knows what to do other than guessing and changing expensive parts.