2002 Saturn SL2 Won't turn over, stalls at idle

When I start it it cranks & chokes, now wont crank at all. I've been having this problem for 2 years. It stalls at stop lights as well unless you keep your foot on the gas in neutral. All the lights go on when you turn the key, so it can't be the battery(which has also been replaced). I've had the fuel injection cleaned & the spark plugs changed with no change.