2000 GT idling at 1800 rpm

[AwPhooey]

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

 

[Bob Hughes]

Are you 100% sure you don't have any vacuum leaks anywheres? Could be a likely culprit, I was having similar problem, that's what mine turned out to be.

 

[Jhussey1280]

Vacuum leak would be my guess. Could even be a crack in the manifold some where. Happened on my Civic actually. Would idle really high then settle down. What was happening was the manifold was heating up and closing the small crack, then after sitting for a few minute is cooled enough to widen up again. Just a thought.

 

[R.J.]

Unplug your IAC when the idle is acting up. If there is no change up or down then the IAC is not working (clean or dirty). If it does affect the idle then put a vac gauge on it, you should be close to 22 at idle.

 

[AwPhooey]

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

 

[Jhussey1280]

Hmm I would never have suspected that since I've never heard of that being a big issue, but glad it's all square now.

 

[mikemora01]

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

what do you mean they replaced a portion of the throttle plate? is that the plate inside the throttle body that opens and closes with throttle. i have been having a hanging idle issue for months and have tried everything above plus much more.