When computer controlled vehicles are first started, they operate on a preset level of information. This is often called CLOSED LOOP. Once the engine reaches operating temperature (Around 210-220 Degrees) The computer functions in OPEN LOOP. The computer takes signals from several sensors around and on the engine, and uses the info to regulate the Spark control and fuel injection. Your problem could be in the actual computer itself. With dealership labor at over $ 100 per hour here in Northern CA, I would be inclined to buy a universal code reader and do a little self diagnosis first.