Engine idles at 2-3,000 rpm after some driving!

[5spd GT]

My '98 has recently had a PI Headswap about 5,000 miles ago, just for some information. The car has 123,xxx miles on it.

However, I do not think it is related to the PI headswap at all, because it just started.

After the car warms up (or what I notice), the car will idle at 2-3,000 rpm while cruising. Then I can come to a stop, and it will take maybe 6-10 seconds and it will finally idle down.

Is this an Maf problem? VSS?

Any ideas or someone that has had similar issues

Other than that, it runs great!

 

[the98stang]

You most likely have a vacuum leak some where. Take some butane and run it over the vacuum lines. If the engine surges (increases in RPM) that's where the leak is.

Only other thing I can think of is the "hanging idle" problem. Does it happen when you put the car in neutral or shift and slowly fall to 800 rpm? Some people blame this on the IAC, so they install a "restrictor plate" on the IAC to solve the problem.

 

[Bad92GT]

Sound almost like a hanging idle problem.. thats really extreme. Mine's not that bad.. the iac plate, EGR delete, exhaust, and intake all helped it to stop

 

[5spd GT]

It sort of just started all of a sudden.

It happens after it is warm it seems like, and I do not think it is a vacuum leak at all.

Sounds like a hanging idle problem, because after a few seconds (7-10) the idle will go down to normal.

Do I just need to clean the IAC?

 

[Bad92GT]

try that.. you do a IAC restrictor?