AwwPhooey

Heya Folks-

Can use some direction on an idle issue I’m having with my 2000 GT.

The background, I took the engine out of my stock A/T 2000 GT (118K) which was totaled due to accident (engine was fine), and put it into the manual GT I own now which was purchased from a buddy (had an engine with 145K, froze due to timing chain issue). I took the bolt on equipment he had on his blown engine and placed it on my stock. This consisted of:

K&N Cold Air Intake
Accufab 70mm
Dragon Polished Upper Intake Plenum

I’ve had the engine in and running for about a month now, and what I’m experiencing is a very high idle at stop (1500 rpm) that lasts about 5 seconds, before dropping down to an unsteady 800 rpm (750 – 850). Doing research on some of the posts here, I went ahead and did the following:

Removed and cleaned throttle body with throttle cleaner. It was dirty but not near as dirty as I’d have expected.
Removed IAC and cleaned out. This was pretty dirty.
Replaced throttle position sensor
Removed and cleaned mass flow sensor using mass flow sensor cleaner
Removed K&N and cleaned
Unhooked battery for 20+ minutes, as I’d read something about resetting PCM this way.
I admit, I need to read and understand more about PCM functionality.

The result is, it now idles even higher at 1800 rpm easy, before dropping down to a steady 1000 rpm after the same 5 seconds. Obviously, this wasn’t the affect I was looking for. A buddy with a similar set up told me to replace IAC rather than clean, as cleaning won’t necessarily do as good a job as having new. I didn't buy one because when I cleaned out my Explorer IAC, it worked perfect after. A new is simple enough to pick up on the way home. BUT, if that doesn't fix the issue, what else should I be thinking of?

Would appreciate any advice you can take the time to give.

Thanks in advance,

Phoo

Fryguy22

Hey there a few questions for ya, say you're creeping along in first gear and your tach is reading 1200 will your car accelerate up to the 1800 rpm mark without putting your foot on the gas? As far as the IAC, I have had two different experiences. The first time in my other mustang, my car wouldn't idle at all it would just die. I tried cleaning the IAC and that didn't help so I replaced it and all was fine. The 2nd time my motor was sticking at 3000 RPMs and I cleaned it out and that did the trick. It really is hit or miss with the IAC. To reset the PCM try unhooking your battery for at least 5 minutes. Next rehook the battery, start your car and let it run for a few minutes. Next turn on your a/c and let the car run for a few minutes. Turn off the a/c and it should be fine, or as close to normal as its gonna get barring any problems. If resetting the pcm doesn't help I'd say start off by replacing the IAC and go from there.

cliffyk

Check the throttle stop screw adjustment--here's how. If too much air is bleeding through the throttle the PCM (via the IAC) will not be able to properly control the idle...

2001Supercharged GT

The high idle could be a vacum leak, you said you swapped motors. There would be a damaged line, or one that is unhooked. This would cause a high idle. After cleaning all those parts it could in theory cause your car to idle higher because it's getting more air and is trying to make up for that by sending more fuel.
I would check the throttle stop screw before checking this.

AwwPhooey

Ok, sorry for the delayed response and thanks everyone for taking the time. Brought it to a shop and they adjusted the throttle angle replaced a portion of the throttle plate. I prolly should have been able to catch these things, but I'm still learning. Comes off the freeway fine now and goes right down to 750.

Thanks again
Phoo