High idle after coming off highway

Well I'm still fighting with a cold start high idle. I have replaced the ISC motor and all the vacuume line etc. etc.
Lately even hot and driving for a few hours when I come off the highway and need to stop at the end of an off ramp the car still wants to idle at 1500rpm some times it will slowly idle down as I drive around, sometimes I need to shut off the engine and wait for 2-3 seconds then start it back up.

Anyone got any idea on what it could be now?
I checked for intake leaks a few different ways and found none,

I was told to replace the idle air valve but I was also told that this would not have anything to do with my idle one the coolant temps were up.

That sounds more like a computer problem taht you need to reset it to fix

My car does this too, except that mine doesn't go away if I shut the car down. I've never really looked into it, but if it's heat related it's going to start getting annoying really soon (hopefully!).

After reading <A HREF="http://207.154.72.181/archives/m/1997/03/19970318.txt/12.html">this post</A> I keep meaning to check out the throttle % signal on my AFC when it happens to see if maybe the throttle plate is somehow sticking open but I always forget.

Hopefully someone out there has solved this one before?

All night my car even hot wanted to run around 2500rpm when first started. It seems anytime you get on the throttle hard taking off or while on the highway at it wants to keep the rpms up high once you slow down

If I rev the car while it is cold, it will rev up to 2500 or 3000 rpm fine and then the revs come back down to normally untill about 1500rpm (then the rpms drop very fast to about 500 rpm) it is like the car just stalls for a second.

I have reset the computer about 100 times but it does nothing.It has never shown a code either .

I was wondering if my timing belt skipped a tooth could this cause it? or would it not run ?
I ask cause I know my tensioner needs replacing.

[ February 26, 2002: Message edited by: Steve Leigh ]

Start by cleaning the throttle body. Remove the egr make sure its working with a vacuum pump, clean the ports . Also remove the IAC there may be a build up of carbon inside.

I would recommend taking carl's advice and making sure everything is clean before anything else. Once you're sure the TB is clean, Fast idle almost always boils down to getting unmetered air from somewhere. I had a similar problem where the idle would scream on startup (2000-3000rpm) but then settle down to normal once the car warmed up. Finally after checking the isc, making sure all intake hoses are tight, capping all the vacuum lines etc etc......eventually I came to the conclusion that it was either a)the egr valve or b) the FIAV.

I picked up a cheap throttle body (without the isc) which is very easy because nobody seems to really want them without the isc and gave it a shot. It did indeed turn out to be a bad FIAV.

[ February 27, 2002: Message edited by: Gary Singletary ]

I will take it off and clean it all that way as soon as I get my bike on the road. Right now the car is my only ride.

Carl or someone

I have an ERG block off plate. should I just throw it on there?

Also this IAC that may have a build up of carbon inside.
What is that? is that the same as the FIAV?

Do I need to remove the throttle position sensor to clean the TB ?

BTW thanks for everyones help

[ February 27, 2002: Message edited by: Steve Leigh ]

Hmmmm I just noticed you have a n/t. As far as I know they don't usually suffer from the major idle woes of the tsi's. My primary guess would still be a dirty TB. If you have an egr block off plate I don't see any reason not to throw it on when you clean the TB. At least you can eliminate that as the problem.