I have a 2000 Saturn SE (4 door) with 79k miles on it. I recently had to replace the transmission. Since then, the car has been idling roughly; it seems to want to cut out on me if I'm sitting in traffic. Yesterday, when I was parked on a slope, I started the car, and it immediately cut off; I started it again, and it cut off again (plenty of gas). I finally was able to get it to stay on after revving it and backing out of the driveway quickly. Do you have any idea what the problem could be??