2000 Mustang GT engine wont stay on!!

I just finished school and decided to buy myself something I always wanted - a Mustang GT. I got it this week and it ran fine until yesterday (But I hadn't really driven it alot because it wasnt plated). The car sat for about 3 days (so I could get it plated) and now the idle is irradic and when I come to a stop sign the car shuts off. I called the previous owner and he said he had never had this happen before. The idle feels as if the car is going to shut off, then it stabilizes a bit and then if I give it gas it revs great but shuts off right away. What could it be?

Thx in advance for any response.

Sounds like a fuel delivery problem. Start off with the cheap and easy and go from there.

Replace the fuel filter. A new one costs less than $20 and should be replaced every 20,000 miles or so. Not hard to do and no special tools necessary.

If that doesn't solve anything, check the fuel pressure at the fuel rail. Not sure of the exact pressures, but should be around 40psi engine running, IIRC. If it is low, check the function of the Fuel Pressure Regulator by removing the vacuum line from it. Fuel line pressure should increase. If not, it is faulty. If it is still reading low pressure and FRP is functioning, your fuel pump may need replacement.

I've tried cleaning the IAC and MAF but no luck nothing has changed. Thanks for the suggestion, i'll try changing those and see what happens.

It could also be the vss sensor, which is located at the tranny. I had this happen and the idle wants to die as soon as you put the clutch in. The vss sensor keeps the idle speed up when you come to a stop.

Good luck....