My girlfriends 92 lumina studders at idle and occasionaly during acceleration. The car still drives fine, and once you get to cruising speed it runs fine. Sitting at idle the exaust smells rich and the car is getting poor gas milage. Ive replaced plugs and wires/fuel filter and air filter with no change. I dont have a fuel pressure tester or that would have been my next step. The fuel filter had nasty gas in it when i poured it into a bottle, and the car sat for a while before she got ahold of it so theres no telling the shape of the tank without droping it (which im trying to avoid unless i have to replace the pump).

Ive put the car on a computer and no trouble codes flash but it did pick up a reading (cant rember what it is ill update tomarow) that kept alternating between rich and lean. Any help would be greatly appretiated as this is our only car.