I just got a 98 mustang gt auto with 82,000 miles. The problem im having is when i rev the engine in park or neutral it revs but stays reved for about a second or two and then goes down. Is it the IAC?

 

IAC, TPS.

 

check your throttle cable, if you have an aftermarket TB, previous owner may have got a bind in the cable... Or, it could be your TPS (black plastic sensore on the TB). That's on good and tight too! LOL. Exactly how long is your engines rpm's staying elevated after you let offa the gas ne way?

 

it's your vehicle.speed.sensor doing it's job.

 

if your talking about when u rev your engine and it looks like it kind of slows down around 2000rpm instead of just falling straight down like a brick , then i think thats normal... mine does that too, and im sure everyone elses does too , this is if im talking about what ur takling about

 

you know when you first turn your car on and the engine isn't warmed up, you can rev your engine and it'll drop really slowly and stop around 1k or even a lil more. i'm sure your baby is ok.