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View Full Version : Anyone have an IAC Fail in the Opposite Direction?


Zack
04-19-2010, 07:37 AM
Most IAC failures lead to stalling and a low idle.

I think I have a sticking IAC, cause it takes forever for the rpm's to drop and anything I do in the programming does not make a difference (to get the rpm's to drop faster)

I have one ordered but I was curious if others has a similar issue? :help:
MM_BKK
04-19-2010, 08:03 AM
What is the lowest rpm that it drops down to?

Were there any physical work done to the car prior or it was working fine and one day the idle rpm won't drop?
Zack
04-19-2010, 08:09 AM
The rpm's get down to what is commanded in the pcm, just takes a few seconds.
Also, it goes dead lean some of the time I take off (from closed throttle) which leads me to believe it is in fact sticking
CBT
04-19-2010, 08:17 AM
My RPM's used to shoot high (enough to make my butthole pucker) and hang a little high on start up. I'd blip the throttle and it would drop down dramatically. Too low, in my opinion. Took everything apart and cleaned the living shite out of everything, took care of the high RPM's.
(The low RPM's were taken care of by your tune:beer:)
The only other time my idle got stuck was when the thin azzed gasket on the CAI fragged and a piece of it got stuck in one of the butterfly's. And blipping the throttle only made it 100% worse! Think I told that story.
I would say call Zack with this issue, but you just happen to be him.:)
n00bkiller944
04-19-2010, 10:38 AM
It happened to one of my friends 1998 Cobra... His RPM's would stay high for wayyyy too long. Sounds just like what is happening to you.
Zack
04-19-2010, 11:43 AM
Just picked up the new one and it definitely rebounds faster than the old one....and the plunger sits higher (to the closed position)

Ill be installing it in a few hours.
mrjones
04-19-2010, 02:30 PM
I've had it on my Mustang. RPMs would stay up high.
Got_1
04-19-2010, 03:35 PM
both of my old box vics had very high idles upon start up...both corrected with a new IAC
MM_BKK
04-19-2010, 06:30 PM
Just picked up the new one and it definitely rebounds faster than the old one....and the plunger sits higher (to the closed position)

Ill be installing it in a few hours.

Your few hours are up. How did it go?



The rpm's get down to what is commanded in the pcm, just takes a few seconds.
Also, it goes dead lean some of the time I take off (from closed throttle) which leads me to believe it is in fact sticking

What is a few seconds and from about what ECT? If the ECT is less than 100* then it could take up to 2-3 minutes to get to the commanded idle RPM. At least that's what my set up does. You could try to zero out all the RPM Adder in the Startup scaler and see if that will reduce rpm flare up upon starting. I did that in one of my tune with PRP and didn't like it, but to each their own. I like mine to roar to life when starting.

I had the dead lean issue too from 700 rpm idle that took me a while to resolve which was not caused by sticking IAC (in my case). It was in the tune.
Zack
04-19-2010, 07:38 PM
I noticed a small difference with the IAC but no cure.

I think its a timing issueand I made a few new tunes to try out in the morning.
I have a HUGE single blade TB that isnt making matters better.
FordNut
04-19-2010, 07:50 PM
When the weather warmed up I noticed mine having an issue with revving up and taking a long time to drop down to normal idle. I reduced the cold start rpm adder and shortened the time a little bit. I tried a few changes, reduce it too much and the car dies.
ImpalaSlayer
04-19-2010, 07:50 PM
I noticed a small difference with the IAC but no cure.

I think its a timing issueand I made a few new tunes to try out in the morning.
I have a HUGE single blade TB that isnt making matters better.
are you sure its closing allt he way? mine did this when it wasnt closing all the way. next time your in it put you foot under the pedal and lift it up to see if the RPMs drop.
1stMerc
04-19-2010, 08:32 PM
Most IAC failures lead to stalling and a low idle.

I think I have a sticking IAC, cause it takes forever for the rpm's to drop and anything I do in the programming does not make a difference (to get the rpm's to drop faster)

I have one ordered but I was curious if others has a similar issue? :help:

Had the same problem with mine. Hanging around 1500 to long coming to a stop. Changed the tune, no more problem.
Zack
04-20-2010, 06:32 AM
Got it fixed....had to lower the timing at low loads to 10 degrees max.

The Dragon TB I have on there is a single blade and is GIGANTIC. You can almost fit 2 soda cans side by side in the inlet. Im tempted to make an IAC restrictor, but it works fine as is so Im leaving it alone.