My son's car started acting up yesterday. It died on his way home. He could start ot but once he shifted into gear ot would stall. Once at home it was ruñning real rough. Did a fuel system cleaning via additives.. ran aliitle better but once in gear it stalled again. Today i came to look at it some more thinking transmission or crank shaft sensor. Car would not idle at all. Hard to start. Now I'm thinking fuel filter or maybe throttle postion sensor.. any ideas would be very helpful.