High idle after replacing IAC valve

[babyjeep]

I'm late to this party...

I've got a high idle problem (on a ZJ) as well which is how I found this thread.

OP mentioned he ordered a new IAC and the plunger seemed longer than the one on the original IAC. One thing I did not realize right away is that the IAC plunger can be manually adjusted. You can rotate it to shorten it, and you should rotate it so it matches the length of your original IAC. Once you install it and start your engine, the idle will be high again, but the PCM will adjust. It will take about a minute and you will see it slowly come down to around 700 RPMs and stay there.

I just joined so I could post this here. I hope it helps someone else.

Meanwhile, my high idle is back ... so perhaps I should not be posting "solutions" just yet

(It appears we can't edit previous comments so I'm adding this update here. Hope it helps.)

Following up on my "high idle is back" comment ...

It appears temperature is important. This time I *warmed up the engine*, then shut it all down, removed IAC, and rotated it to just below 1 1/8" again. High idle seems to be resolved now.

 

[DougT]

Ok - gotcha. Cleaning my TB and the IAC and orifice is what led me to this point (well - ultimately it was that damn whistling; it's so LOUD when it happens). I changed out to the new IAC valve because I thought maybe the whistling had to do with it sticking or something of that matter. After which, I had the high rpms from the new valve...



Ok - I'll swap back to it, hopefully later tonight if I can find the time. Time is my issue right now, due to my other concerns. As far as the actual gasket, I'll have to find someplace that sells them; when I picked up the new IAC from AutoZone, I tried to get the orifice gasket too, but they had nothing in stock - not even at other AutoZones (is this gasket unobtainium?). So for now, I'll run on the cardboard gasket until I can find a real one.



That I understand, but right now I am getting the high idle from the new IAC, where the plunger is much shorter (by about 1/4 to 1/3 of an inch) than the old IAC's plunger. It's so short, it could be considered "wide open" as it isn't plugging the orifice at all, whereas the old one almost completely plugged it, as far as I could tell when I mated things up.

Also - another thing I noticed - on the old IAC the "ears" (where the screws mount it to the orifice body) are bent, and it doesn't completely mate to the orifice body - there's a gap; the new IAC valve's ears are not bent, and the whole unit mates tightly, with no gap between. I am wondering if that gap is part of my whistling issue?

Regardless, I'll swap it back. I'll probably get the whistling issue again, but at least my idle won't be high...

I just replaced the IAC on my 2004 Jeep Wrangler TJ and when I started it up the idle was high (~ 1500 - 1800) with a CEL. I didn't have any whistling though. I did notice that I had a small gap, even when tightened down between the IAC and TB. Pulled out the new IAC and placed the old IAC in and it seated up against the TB with no gap. Checked the o-rings and the new IAC o-ring was about twice as thick as the old one. Swapped o-rings between the two IACs and restarted the engine. The idle was back down to normal and no CEL.