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Old 04-24-2007, 12:28 AM   #1
Asterix
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Default High Idle and P1507 cel - Need new IACV?

Hi all,

2003 WRX wagon with 72K miles. It warmed up here very nicely in Boston today so I decided to go for a spin during lunch. On my way back my car starting idling higher at each stoplight until it was just over 3000 RPM all the time. I have noticed this problem over the winter a couple of times, but it has never happened in such a short period of time like today and usually disappeared after I got on the highway for a short while. Today it did not go away and as soon as I got back on to local roads the car idled at almost 3000 RPM again, though it would fluctuate down a bit and then go back up.

I pulled over in a parking lot near work and hooked up my Cobb Accessport (flashed to Stage 1, but running in stock mode right now) to see if resetting the ECU would clear up the idle issue. When I restarted the car the check engine light came on and the Accessport read it as P1507. The car still idles high and was a bit jerky when applying gas and letting off the the clutch in 1st gear.

From searching on the forums it sounds like my IACV may have gone bad, but I just wanted to see if anyone else has a second opinion on this.

I'm going to try and avoid the dealership on this and see if the garage next to my office can look at the problem for me. If it comes down to replacing the IACV and the local garage cannot supply the part, what's my best option for finding one online? Subaruparts.com?

Thx!
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Last edited by Asterix; 05-08-2007 at 11:10 AM.
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Old 04-24-2007, 12:32 AM   #2
Thran
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Well first i wouldnt jump the gun, i had the exact problem you did, and found out it was my throttle body at the end

but anyways, i would clean first the IAC and see if that helps out, i would get another gasket just in case due to them breaking when ur putting it on, that might fix your problem right off the bat. If it doesnt, then look for some leaks of some short (take a look at ur TB see if there is a crack) check ur intercooler hoses and all other vaccum lines

If nothing helps then replace the iac, best thing to do is get one from online, i picked up one with a TB

GL bro
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Old 04-24-2007, 11:31 PM   #3
turbo_rob
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Default Iac

hey what is an IAC exactly ? and how do you clean it. i have the same problem but worse it goes up to 4000 idle lol.
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Old 04-25-2007, 01:24 AM   #4
fast71
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Quote:
Originally Posted by turbo_rob View Post
hey what is an IAC exactly ? and how do you clean it. i have the same problem but worse it goes up to 4000 idle lol.


http://forums.nasioc.com/forums/show...=iacv+cleaning
I tried this but, didn't work. maybe you'll have better luck than me.
here's where I brought the new one.
http://www.subarupartsforyou.com/cp_...hp?partid=7165
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Old 05-08-2007, 11:09 AM   #5
Asterix
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Well, I replaced the IACV (got it from subaruparts.com with the new gasket) after cleaning it did not work. Although I still had some rough idling at first, after about 50 highway miles the problem seemed to have gone away... until this morning.

It is getting up to about 80 degrees today and the morning commute here in Boston was worse than usual. After about 15 minutes of creeping along in 1st and 2nd gear, idling and then more creeping I noticed the RPMs at idle slowly increasing. They topped out at around 2000-2200, which is not as bad as before but every once in a while it would drop suddenly down to 1500 RPM, causing the car to almost shudder. It did this about a dozen times and finally the check engine light came on with the P1507 code again. I'm not sure what is going on now and may suck it up for a trip to the dealership for a diagnosis from them.
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Old 06-12-2007, 07:31 PM   #6
MK19
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This is the 2d IACV I have had on the car PLUS cleaning the already clean valve assy. didn't clear my CEL nor my idle issues. Does anyone have a P/N for the neutral position switch? If I had a voltmeter, the switch can be tested for ohm resistance to see if it is bad- but for $30, I'll replace it

Another odd issue of note is that my CEL comes and goes. I did the IACV coolant bypass mod 3 years ago, so I doubting this has anything to do with the issue. Car still idles horribly tho.
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Old 06-15-2007, 09:06 AM   #7
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I cleaned my IACV again last night- even let it soak overnight and still, no resolution. I am thinking that it may very well be the neutral position switch. Does anyone have a P/N for this on the STi 6 speed?
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Old 06-15-2007, 09:11 AM   #8
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Does it do this with the clutch in OR out? How about in gear / out of gear?
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Old 06-15-2007, 09:15 AM   #9
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Quote:
Originally Posted by Porter View Post
Does it do this with the clutch in OR out? How about in gear / out of gear?
In and Out, in gear and out of gear. Start the car up early am- idle goes to ~1500 and generally bounces up to ~2000 and then back down with no CEL. After a few minutes of driving, pull up to a stop light and the CEL comes on and the idle begins to stumble more and become much more erratic. Under cruising speeds on the highway, the issue is non-existent- except for the CEL remaining on- the car drives and operates just fine.
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Old 06-15-2007, 09:26 AM   #10
Hooligan_22
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Man, this sounds just like a vacuum leak on a MAP car.

Shot in the dark - check for boost leaks yet?
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Old 06-15-2007, 09:28 AM   #11
MK19
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Quote:
Originally Posted by Hooligan_22 View Post
Man, this sounds just like a vacuum leak on a MAP car.

Shot in the dark - check for boost leaks yet?
No, I am gonna pour over the car sometime this weekend when I have time. I agree tho, it does act like a vacuum leak. Odd that it throws the P1507 code tho- and that the CEL comes and goes.
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Old 06-15-2007, 09:47 AM   #12
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Did you try loosening the cruise control cable? That's definitely an issue on the 04/05s, and its free so it can't hurt to try.
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Old 06-15-2007, 09:50 AM   #13
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Quote:
Originally Posted by TurbojonLS View Post
Did you try loosening the cruise control cable? That's definitely an issue on the 04/05s, and its free so it can't hurt to try.
I sprayed them down and messed with the linkage- didn't appear to have any effect, but I will remove both cables today and see if it results in anything. I suppose it is possible that the T/B has some kind of issue, can't rule anything out at this point.
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Old 06-15-2007, 09:52 AM   #14
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It sounds like a vacuum leak to me too. IAC is going wide open to keep the car from stalling.
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Old 06-15-2007, 09:56 AM   #15
MK19
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Quote:
Originally Posted by Porter View Post
It sounds like a vacuum leak to me too. IAC is going wide open to keep the car from stalling.
Is that anything like WOT?
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Old 06-15-2007, 12:58 PM   #16
MasterKwan
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Common technique to find a vacuum leak is get some gum cutter spray and spray it around things like joints and the IAC. If the idle picks up/smooths out. You found your leak.

One guy here reported that he hydrolocked his own motor by not replacing the IAC gasket. Coolant leaked from the IAC into the intake tract. Just something to think about. It's made me wary of messing with the IAC.
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Old 06-15-2007, 01:38 PM   #17
Hooligan_22
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That leak check technique really works well, but I usually use something like carb cleaner.
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Old 06-19-2007, 12:21 PM   #18
MK19
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I checked all my hoses last night and while I didn't use the carb cleaner method, no loose or damaged hoses that I could find. I will give the carb cleaner method a shot tonight, as I have used similar methods in the past. I am just wondering if it is possibly a bad IACV again???!! I wonder what is causing my car to kill them if this is the case. If I can't get a resolution by Sat- it goes to the dealership- I am tired of fixing this damn car... and that's why it's for sale.
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Old 06-19-2007, 10:26 PM   #19
bri619123
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this probably wont help but that happend to me when i replaced my DP but was still in stage 1, once i flashed to stage 2 it fixed the problem...
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Old 07-03-2007, 08:17 AM   #20
MK19
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STILL running the same. I have to believe at this point it is the IACV. It is just so odd that if the car stays below 1800 RPM, the CEL won't go off and put the car into the crazy limp mode, yet the idle will still hover from 1000-1500 and it is running WAYYYY rich. I am going to try and make an appt. to drop it off at the dealer and get this diagnosed at least. I am sure they'll confirm what I am already thinking tho.
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Old 07-08-2007, 07:46 AM   #21
Pacobeagle
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The unfortunate part is that this is one of those problems that you'll have to check each individual part. Most technicians won't do that because it takes time.

I'll see what I can find. Again, it's a V7 motor with it's own ECU?
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Old 07-08-2007, 07:52 AM   #22
Pacobeagle
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One question to all of you guys is what degree T-stat are you guys running. Maybe the ECU's coolant temp sensor thinks that the vehicle is still cold and so the IAC is commanded to run as if under "startup" condition. Just a thought.
Has anyone tried to drain and fill the coolant. Add some of the Subaru Coolant Conditioner. I'm not sure if this will help, but sometimes it's the general maintenance that people forget and then blame parts without cause
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Old 07-08-2007, 08:50 AM   #23
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I'm actually running a Zerosports "Zero-cool" T-stat and straight water- no anti-freeze at all. Could these 2 be the issue? Do you think going back to a stock t-stat will help? With the PWR radiator, straight water and the zero-cool, the car runs rather cool, but I Have seen water temps hit 185 at idle. This is perplexing...
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Old 07-08-2007, 09:36 AM   #24
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Hell, as cheap as a stock t-stat is, and as easy it is to access, it just may be worth a shot. 50/50 mix coolant and water would be ideal too!!!
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Old 08-11-2007, 08:31 PM   #25
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Quote:
Originally Posted by Pacobeagle View Post
One question to all of you guys is what degree T-stat are you guys running. Maybe the ECU's coolant temp sensor thinks that the vehicle is still cold and so the IAC is commanded to run as if under "startup" condition. Just a thought.
Has anyone tried to drain and fill the coolant. Add some of the Subaru Coolant Conditioner. I'm not sure if this will help, but sometimes it's the general maintenance that people forget and then blame parts without cause
The ZeroSports t-stat was bad. Took it out and had Sarah test it- water hit 190 degrees and it still never opened (should have at 160). Fail. So I got an OE replacement t-stat, refilled with 70/30 mix of water/coolant and a bottle of water wetter.

Also checked the neutral position switch- it seems like I am getting an accurate reading at the switch so I am going to check up top at the harness like the manual recommends and get back to you all on results just to be sure. I'm also going to spray check for leaks- this is making me crazy and I don't want to buy a $250 valve if I don't have to.

Last edited by MK19; 08-11-2007 at 08:49 PM.
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