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Old 06-10-2016, 05:48 PM   #1
AeroBullet
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Exclamation Hot weather = Fast Idle

Car is 2005 92x Aero, same as WRX in every way.

For the last 5 years I have been trying to get this problem solved and now my wife wants me to get it solved or get rid of the car, cuz it is driving me crazy and making me less cool to be around.I kind of agree with her, but I love my car.

Here is the main thing. In traffic on a hot day, I'm totally f'ing hosed because the idle will climb and climb and climb until it is at 5500 RPM, at which point I have to pull over and lift the hood to let it cool off, then repeat. The slower I travel the worse it gets. Any speed below 35 mph will eventually have the same effect, like crossing town stopping at traffic lights for 30 minutes. Once the engine gets up to temp on a hot day, anything but sustained highway speeds will have the engine racing.

This happened in stock form and then got much worse with a Cobb downpipe and AP.

Basically, as long as fast or cool air is going into the hood scoop I,m good.

I'm in Ohio so it gets really cold in the winter and really hot in the summer. This only happens when the temps are 70+ or if I'm stuck in traffic. If I drive around and then park for 15 mins

First thing I did was to loosen the cruise control cable after reading WRX.net forums.
http://www.clubwrx.net/forums/engine...-cc-cable.html This had no effect, same problem.

Next, I did the some heat abatement in the engine bay.
I wrapped the turbo, downpipe and cat 2x in lava heat wrap from DEI.
I put put a metal heat "curtain" hung next to/ under the intercoooler to stop hot DP from soaking it.
I cleaned the intake and IAC, which seemed to actually work for a little while, then back to racing idle again.

Here is what I think: (please tell me what you think)
The IAC is getting gummed up with oil from the PCV system. This I know cuz I cleaned it once already and problem was solved for a tankful. In cold weather its fine and IAC (even dirty) operates fine, but in warmer temps the metal valve expands and tends to stick in the open position with the gummy oil in there.

My next step is to install an air-oil separator, but I'm not spending $250 for a "good" one. I'd love the $380 Crawford AOS, but don't think I can justify it. So I'm looking to heavily modify a catch can mounted near the turbo to keep it hot and working.
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Old 06-10-2016, 10:29 PM   #2
Brother EddieJ.
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2004 wrx
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It's your cruise control unit. It's know To pull the idle cord when it gets hot. Try unhooking the line to the cc and see it that helps. If it doesn't you have another issue.
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Old 06-10-2016, 11:44 PM   #3
brewster_fwrxster
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My ej20 does the same thing, does not have cruise control
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Old 06-11-2016, 01:39 AM   #4
victomdetroit
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second the cruise control line. the heat shield on the line contracts and pulls the cable enough to open the throttle.
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Old 06-11-2016, 11:13 AM   #5
AeroBullet
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Default Ruled out cruise

Brewster and myself can confirm this is not the cruise control. I disconnected mine and it still did it. He has none and his does it.
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Old 06-15-2016, 01:15 PM   #6
86Dreams
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What is this? An
injector laying contest?

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just replace your iacv?
replace the pcv valve?
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Old 06-15-2016, 01:17 PM   #7
brewster_fwrxster
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I've cleaned out my IACV twice and installed a new PCV. Still does it. I just have to guess its something with the IAT in the MAF, as I have a SPT intake and no box/shroud. I think the sommbich just gets really heat soaked.
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Old 06-15-2016, 07:53 PM   #8
hoffmanEstates
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With high idle can you get your fingers around the throttle and see if the cable has tension on it or is free/slight limp.

With the AP can you read intake temp?
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Old 06-15-2016, 07:54 PM   #9
hoffmanEstates
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Quote:
Originally Posted by brewster_fwrxster View Post
I've cleaned out my IACV twice and installed a new PCV. Still does it. I just have to guess its something with the IAT in the MAF, as I have a SPT intake and no box/shroud. I think the sommbich just gets really heat soaked.
Sometimes cleaning doesnt work.

Mine failed and i just needed a new one
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Old 06-16-2016, 09:58 AM   #10
AeroBullet
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Quote:
Originally Posted by hoffmanEstates View Post
With high idle can you get your fingers around the throttle and see if the cable has tension on it or is free/slight limp.

With the AP can you read intake temp?
Its got slack just like the cruise cable. Last summer my AP read the intake temp at about 100 on a hot day when it was revving. If I remember correctly.

My next approach is to clean out the intake path, MAF, IAC, and install a catch can oil separator to the PCV lines.

Last edited by AeroBullet; 06-16-2016 at 10:06 AM.
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Old 06-16-2016, 10:04 AM   #11
AeroBullet
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When IAC failed, what was the symptom?

Mine works fine until it gets hot outside. Cleaning fixed it for a bit, so I think I just need to keep the oil out of it with a catch can.
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Old 06-17-2016, 05:51 PM   #12
hoffmanEstates
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Quote:
Originally Posted by AeroBullet View Post
Its got slack just like the cruise cable. Last summer my AP read the intake temp at about 100 on a hot day when it was revving. If I remember correctly.

My next approach is to clean out the intake path, MAF, IAC, and install a catch can oil separator to the PCV lines.
I have nevwr had this such of an extent of idle high.

And i am 220k and no catch can
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Old 06-21-2016, 09:42 AM   #13
AeroBullet
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Quote:
Originally Posted by hoffmanEstates View Post
I have nevwr had this such of an extent of idle high.

And i am 220k and no catch can
Can you tell me what your IAC was doing that you thought it needed replaced? How much wa$ it?
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Old 06-21-2016, 09:55 AM   #14
hoffmanEstates
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Quote:
Originally Posted by AeroBullet View Post
Can you tell me what your IAC was doing that you thought it needed replaced? How much wa$ it?
I had the idle problem where it run a few hundred higher all the time.

I cleaned and installed new gasket to help only few days.

Called local speed shop and they advised me to replace it. So took it there and they placed a good working used one. Till this day it runs proper.
Cost was not much as it was used part
New gasket
Install labor.

Every oil change i clean my air filter amd use crc maf cleaner. It does help especially that crc maf cleaner
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