98 mustang gt. starts then dies or rough idle at 500rpm

Drove it on sunday, ran perfect, went to start it up monday morning, and it started up, then started sputtering, hovered around 500rpm, then died.. I tried starting it a few more times, could get it to idle, but still at 500 rpms and very rough.. I changed the plugs today, still does it.. I don't understand how it can just go from running fine one day to this the next. Any suggestions

There are a lot of things that can cause that. You changed the plugs so you know thats not the problem. You still need to check fuel pressure. If you have not changed your fuel filter its time for that as well. Its a canister, should be located under the driver side frame or in the rear center near the gas tank. You'll need a special tool. Have you used poor quality gas? Its really tough to diagnose over a computer but start with those and see what you get. Does it make any suction noises? maybe you just knocked a vacuum hose loose. Hope this helps.

Thanks. I fixed the problem the other day.. It was the Idle Air Control Valve. Put a new one on, it started up stronger than ever.