High Idle *doesn't exactly match tps symptoms*

[CarverSVO]

First off, I know this issue has been covered a few dozen times here and I've searched around a lot about this. So if I missed something and this has been covered already then I apologize.

Here's the problem. I have a high idle issue where it stays between 1800-2100 rpm once I touch the throttle after start up. At first I figured it was the oh so common tps problem, but it doesn't show the same symptoms as that. I don't get any code 23, the quick key off and on has no effect, and if I wiggle the IAC harness it settles back down until I touch the throttle again. Also, when I unplug the IAC when it is at the normal idle there's no effect, so it stays at 1100 with the idle air control disconnected. I also thought that it might be a vacuum leak, but that doesn't fit with how it surges only after I touch the throttle.

So far, signs point to the idle air control. But like I've read dozens of times here that's usually not the problem. The only thing I can think of is that the guy who put in the new motor painted the throttle body, IAC, TPS, and intake which may have caused some paint to make something stick that shouldn't. But that's just a random guess. If the idle air control is bad, would one from a 94-95 throttle body work as a replacement? I still have the larger TB sitting around waiting for me to get the intake ported.

-Edit- I slapped on the IAC from the 94-95 TB and it's still the same. Even with it disconnected the idle stays around 1200. Any ideas?

[CarverSVO]

Update: I just tried to pull codes again and this time I got #34. IIRC that's something about the EGR. So could that be causing a high idle?

[blackpheonix]

the first thing that would be wondering about is the wiring to the iac. If you wiggle and it changes something, it time to pull out the soldering gun and find that bad wire. I would unwrap the wires frome the iac for about 10 inches up also check on your wires leading to the distributer module and check those about 2 feeet up the line.

[CarverSVO]

Here's my application for dumbest question of the year:

Is this supposed to be connected?

-edit- Well even though I'm sure it helped to put that back in place, the idle is still off. And as it turns out playing with the harness doesn't do anything. For some reason it randomly drops back down for a moment even if I don't touch anything, but only if I haven't driven it and only let it warm up. So, the idle still surges to 2000rpm after I touch the throttle but momemtarily falls at times without me touching anything. And disconnecting the IAC has no effect whatsoever, even with a different unit. This is confusing.

[Todd]

Just another idea to toy with. I had a similar issue that turned out to be the coolant temp sensor. $19 at Advanced and 10 min to change. I thought of everything before I found the real problem.

http://www.svoca.com/forum/showthread.php?t=12410&highlight=FPR

[tripice351]

x2 for the coolant temp sensor, it gave me a high idle too.
Careful when removing it tho, it's made out of flippin' plastic. Gonna need to remove the upper intake, and a 1" or 25mm deep socket, IIRC.. It was original, as far as I know. Mine broke, had to drill and try to easy-out it.. no luck. Ended up drilling the whole thing out. Thought we got all the pieces out, until we recently pulled the lower intake.. small pile of plastic sitting nicely in the coolant passage. Thank goodness the Ford replacement is metal..

[Todd]

I was able to take out my sensor without taking off the intake by using a swivel. Each car will be different. Some like their parts and don't want to turn lose of them. Which ever way you do it.Just take it slow and easy.
Again, this may not be your problem. Just an idea.

[chuck nasty]

thanks for the info. i've been chasing that problem for a while. i'll change my temp sensor. what do you guys think about a vacume leak? it just so happens that i work at a Ford dealer, so i took it upon myself to use the smoke machine to find out if i had some leaks. my egr valve along with other hoses were found faulty (shame on them). by the way i have an 84 svo, 88 tc (with a lot of mods), 01 v6 mustang and 04 mach 1.

[CarverSVO]

Sorry to bump this after so long, but I've finally fixed part of the problem and figured I'd give a conclusion to this. As it turns out the surging idle was due to a crack, which turned into a break, in the egr valve. With a little help from a can of carb cleaner and a lot of help from member BDBYS59 I have that sorted out. The idle still sticks at around 1500, but it no longer surges or overheats which was my main concern. So I have part of the high idle fixed, and in the next month I'll finally have more time to pinpoint the remaining bugs. I'm happy.