My car was running fine, in fact great. We stopped to get gas and I put in about 5 gallons (short on cash). When I left the station, the car started sputtering at low RPM's. When the car is idol it almost stalls out then when you get the car moving, the car will almost stall then sputter its way up to speed. Once you get to about 2k RPM's the car will start to drive okay. The check engine light has come on and it stays lit while the car is on.
What is the issue?