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Old 05-21-2004, 04:57 PM   #1
Lo0mis
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Join Date: Nov 2001
Location: Valencia CA
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2000 2.5 RS
BRP

Question Stuck IAC?

Sometimes when I pull off the freeway, my idle gets stuck up around ~2000 rpms. The only way I can get it back down is by putting it in gear holding the breaks, and slowly letting the clutch out, basically "pulling" the idle back down. Sometimes it'll stall out, and sometimes it jumps right back up to 2000, but after a little while I can usually get it to normalize itself. Any Ideas?
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Old 05-21-2004, 09:04 PM   #2
25rstautoxr
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Arent you running some kind of engine management?

If you are adjust your overrun vaccuum to a lesser number

later
chris
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Old 05-22-2004, 01:09 PM   #3
Unsung Boxer
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I am having a similiar problem, and it happens very intermitantly. You are not actually bringing down the idle, your just imposing a load on the engine obviously.

I also suspect that my IAC motor is taking a dump. Its an electrically controlled valve that will allow minor air flow to enter the engine while the throttle blade is shut (when TPS sensor goes to 0)

a couple things can be happening here:

1. Air is entering the system somewhere else, thus the IAC motor will go fully closed to compensate, but Idle will still go to high. This is vacuum leak.

2. The Throttle blade is not fully shutting, thus air is going directly past the blade, and again, IAC has no control.

3. The IAC is dirty/clogged. It cannot open and close the way the ECU is controlling it to.

4. The IAC electric motor is not working properly. Like any electrical componant, it can fail. A good test is the tap test. If you can duplicate the problem at home, take a hammer and tap lightly on top of the IAC motor. If it suddenly comes to life, or the symptom changes, u know the motor is shotty, and should be replaced. Be careful not to brake the motor while doing this.

In all cases the engine will likely throw a CEL after 5-10 seconds of high idle.

Let me know what happens for you with this situation, as I am having difficulty with mine.

-Jake
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Old 05-23-2004, 04:40 PM   #4
Lo0mis
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Thanks for the tips guys. I'll let you know what I find.
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Old 05-25-2004, 04:07 PM   #5
Sidwindr
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my 99 RST is doing the same thing
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Old 05-25-2004, 11:48 PM   #6
no-coast-punk
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I just learned a trick today from one of the master techs here. It doesn't work on all manufacturers, but it works on diverse enough vehicles for me to post this here.

1. Get in the car, turn the key to the On position, but do not start the car

2. Count to 10 slowly

3. turn the key off

Repeat the above steps 2 more times (for a total of 3)

on the 4'th time, instead of simply turning the key to the "on" position, start the motor and let it idle for 1 minute or so.

Sometimes the ECU forgets where the IAC motor is positioned and has no idea how much air it is letting into the motor (way too much air will give you your insane idle). This process makes the ECU re-learn the IAC position. Keep in mind this might not work (it works on every American vehicle out there, plus Toyotas, but it doesn't work on Hondas). I have never heard of anybody trying this on a subie, let us know if it works.
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Old 05-26-2004, 01:49 AM   #7
subiekid
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ok, you can change the amount of air that the IAC lets in by rotating it, there will be 2 screws on the IAC, loosen them, and you can rotate it, its different for how much air goes in, so you might have to rotate one way and then try the other.

hope this helps.
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Old 05-26-2004, 11:16 AM   #8
Lo0mis
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That would work if it was doing it all the time, but this problem doesn't happen all the time. If fact it hasn't occurred since I started this thread. I've been waiting for it to happen so I can test some ideas out and so far nothing.
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Old 05-26-2004, 03:44 PM   #9
subiekid
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Hmm, i had this problem when i did an ecu swap, but was just that the IAC let in too much air. I have no idea what would cause it to change like that.
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Old 05-26-2004, 05:50 PM   #10
HOK
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interesting this has been happening to me for like 2 years... every intermitten... sometimes 6 mths apart, sometimes twice a week... I havn't been driving the car for the last 5 months.

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Old 05-26-2004, 06:27 PM   #11
benjaminetanyahoo
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Well I don't know if this is related, but I have a stranger problem. I justed changed my Fuel Pressure Regulator today, no change in my crappy idle. Ok I can accept that, maybe it's because the hybrid motor and stock ecu. Aight whatever, well BY ACCIDENT I forget to connect a vacuum tube on the top of my intake mani start the car up, and the car idles like a champ. Of course you hear the sound of air leaving the the port off the vacuum tube. I let the car run for a while to see if it was just a fluke, nope, press the gas, goes right back where it was supposed to be and good idle again. I plug the hole with my finger, and boom back to bad idle, plug it up permanently and get on the gas, bad idle. Any ideas? A bad idle control valve all together or what? This is funky
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Old 05-26-2004, 06:43 PM   #12
HOK
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try that reset trick that no coast posted sounds like that
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Old 05-26-2004, 06:50 PM   #13
benjaminetanyahoo
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Didn't work at all, but it's gotta be the Vortech RRFPR.

Here is my thinking, somebody correct if I am wrong please. I disconnected the vacuum tube for the Vortech and it idles great. The Vortech uses vacuum to control fuel pressure regulator, without vacuum it's basically getting bypass aka just running a single line for your fuel return hose. When connected it idles like crap again and the vortech is now controlling the fuel pressure back for fuel return. I will get a fuel line to test it out to make sure 100% but I think that is it.

Anybody?

Last edited by FutureSTIer; 05-26-2004 at 07:52 PM.
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