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Old 01-21-2012, 04:36 AM   #1
aberg12012
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Default Rough Idle When Half Warmed Up (Cold Weather) 2008 WRX

Is this normal? Or even common? I've had cars run like crap when it's cold, but this seems weird to me...

We got our first real cold spell here (between about -5 and +5 F) and I started to notice that between about 130 and 170 coolant temps the motor runs really rough at idle. It feels like it's missing and about to die, however it never does. It starts and idles great totally cold, but as soon as I drive a half mile or so and come to a stop (when it's now trying to idle down to about 800 rpm) it starts to miss. It goes away once the motor is fully warmed up after a good 5 or 10 minutes of driving. I'm pretty sure it's been doing this since the first winter I've owned it, but for whatever reason I never really payed attention to it till this past few days. (Since it's something that only occurs in a narrow window.)

After doing some open source logging I suspected a vacuum leak, however I didn't find any. The car is stock except for a K&N stock replacement air filter. With the stock tune it's a little better, however in logging it still shows a lot of misfires in that temp range until it reaches about 180 degrees.

As far as I've noticed it doesn't do this until it's below about 20 degrees out, and by the time it reaches sub-zero it's something even my totally non-mechanical minded wife would notice. (Not to pick on my wife, just making a point that it's very obvious when it becomes this cold.)

I realize there's probably a couple dozen possibilities, but anyone ever had this issue before?
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Old 01-21-2012, 08:41 AM   #2
424wrx
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same here. on my 08, im vf52 swapped with a stage 3 map. i get a rough idle coming to a stop after starting the car in the cold. ie,first stop sign,stop light. after that is seems to return to normal. in for answers as well.
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Old 01-21-2012, 06:31 PM   #3
mitchkeller87
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I have the same problem on my 08. I am heavily modified and I think the cold air intake is putting to cold of air into the motor. Once the car warms up completely it runs fine. Better let it run 10-15 minutes to stop this from happening.
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Old 01-21-2012, 09:18 PM   #4
Matt08WRX
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I noticed it when I was stage 2 on my TD04 but since i changed everything (same intake and dp though) it doesnt do it anymore.
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Old 01-22-2012, 06:20 PM   #5
mod maniac
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Mine was doing that too it would die first stop sign not before not after. rolled that car before I figured it out, that was a 02.
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Old 01-24-2012, 06:26 AM   #6
aberg12012
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Good to hear I'm not the only one. It didn't really worry me much till it threw the cel while i let it spit and sputter while i was under the hood.

I'm guessing the mapping just is set to idle down too soon in the extreme cold. If i go back to my stage 1 tune (i forgot how bad the stock tune is till reflashing it last week lol) ill just adjust the idle tables accordingly so it doesn't idle down so low till its warmed up more.
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Old 01-24-2012, 09:53 AM   #7
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Mine does the same thing....even got multiple misfire codes and a lean code when it dropped down into the low teens for me...scared the crap out of me.

I've read that it could be caused by the gasket between the motor and the intake manifold. Normally only an 08 problem. As the car warms up the gasket expands resulting in a small gap that goes away once the car is fully warmed up and everything else is lined up again(might be an issue with the plastic mainifold...everything else expands much faster causing the issue). Apperently they changed gasket material in 09 to prevent this.

I let my car warm up for a good 10min before I drive it in very cold weather now.
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Old 01-24-2012, 10:28 PM   #8
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Do you get any codes when is misfires? (P0301, P0302, P0303, P0304)

The Legacy engine has bad manifold to tumbler gaskets that cause the exact issue you are experienceing. The updated OEM replacements have square edges and are taller. The WRX are suposed to have a betterer design gasket. But it might share this common gasket in early models. I changed mine in 2 hours. The problem went away.

Check your intake manifold and if you have these orange rubber tabs sticking out, you need your gaskets replaced


This is the new thicker gasket:







This is the LGT thread: http://legacygt.com/forums/showthrea...09-155325.html

Last edited by forpointsex; 01-24-2012 at 11:02 PM.
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Old 01-25-2012, 12:25 AM   #9
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Quote:
Originally Posted by forpointsex View Post
Do you get any codes when is misfires? (P0301, P0302, P0303, P0304)
Yea the one time mine threw cel's it was 0301, 2 and 3. But never on #4. For some reason #4 never shows misfires in this condition. I have lots of logs from the event... i was logging at the time it threw the cel and it hit a 10 count of misfires which I'm guessing is the trigger for the missfire cel codes.
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Old 01-25-2012, 11:15 AM   #10
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After searching for days I have found a thread that has the closest thing to an answer on why my WRX is doing the same. I figure it was just mad at me because I have been threatening to trade it in for a STI. Any way Ill mention the gasket thing to subaru when they look at it next monday.

-#s
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Old 01-25-2012, 08:19 PM   #11
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I have a 2008 with the same exact issue. I was up in NH in the cold when I first saw it. Threw a bunch of misfire codes and almost cried lol. Running Torqued Performance stage 3.52 at the moment with Perrin CAI. Saw a thread a while back about the intake manifold gaskets. Anyone try this yet? Was it a fix?
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Old 01-25-2012, 08:44 PM   #12
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Quote:
Originally Posted by BlackLabelFox View Post
I have a 2008 with the same exact issue. I was up in NH in the cold when I first saw it. Threw a bunch of misfire codes and almost cried lol. Running Torqued Performance stage 3.52 at the moment with Perrin CAI. Saw a thread a while back about the intake manifold gaskets. Anyone try this yet? Was it a fix?
im running a vf52 swap and the same map as you. i get this problem too. after the car warms up it seems fine.
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Old 02-05-2012, 12:59 PM   #13
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Thank you forpointsex!! I've been having this exact issue (08 WRX). I had this issue with no mods other than a CBE and scared the crap out of me. Now that I installed TBE, wide-band sensor, and A/F gauge it shows an insane lean condition (AFR of 17 to 18.5) when it is stumbling at a stop-light/stop-sign. I'll look into the gasket as well and see if that fixes it. Thanks again for the post!!
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Old 02-09-2012, 01:30 PM   #14
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Just had my gaskets replaced at subaru this afternoon, will see first thing tomorrow if it fixed my idling problem...seems to be idling fine now but will be able to really first cold start of the morning...
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Old 02-09-2012, 02:56 PM   #15
BlackLabelFox
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Thanks for the update. If it works I'll be doing it soon too. Did you just ask them to throw in upgrades gaskets and they knew what you were talking about?
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Old 02-10-2012, 07:17 AM   #16
08BlackWRXCT
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Ok well here is the morning update....it worked!

No more rough idle, very smooth idle actually, it actually idles better now too when its all warmed up as well!

Well i went in tuesday afternoon telling them about my rough idling problems, i told them i saw online here and at dedicated 3g wrx site that the gaskets were more than likely the problem causing this idling issue...the shop foreman, new about the issue, he said he has done about 4-5 of them ...so the next day they replaced them free of charge under warranty, even with my stage 2 stuff installed including my front mount... so happy right now!
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Old 02-10-2012, 07:35 AM   #17
BlackLabelFox
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You are now my hero haha
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Old 02-10-2012, 09:05 AM   #18
forpointsex
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Do you see your "bad" gaskets?

Were they like the Legacy type:


Or the WRX/STI type:

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Old 02-10-2012, 12:40 PM   #19
08BlackWRXCT
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i didnt actually see them no, they are the legacy type tho, i could tell by the tab...they replaced them with the new thicker ones mentioned above...
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Old 03-06-2012, 02:49 PM   #20
anthony12052
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my intake manifold has black tabs sticking out, but my 08 has this same rough idle when its cold out....
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Old 03-06-2012, 05:39 PM   #21
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my sti idles lil rough for first few mins when it was kept outside in cold...after keeping it in garage I found it idles fine. So I can atleast confirm the cold has something to do with it
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Old 06-21-2012, 12:35 AM   #22
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anthony12052, have you found out what the issue is? i have the same car, same issue, but the dealer cant seem to figure it out. i have a rough idle at times, even when warm, also hesitation and sputtering. no cel's, just changed plugs, still nothing. any ideas???
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Old 06-21-2012, 07:45 AM   #23
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I have a 08 with a vf52 swap and all the works....had this same exact issue...and it was the gaskets between the motor and intake manifold after replacing all the gaskets the issue was corrected
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Old 06-21-2012, 10:56 AM   #24
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tgraci, thanks for the reply. looks like ill be doing that this weekend then. im taking it if for a smoke test today at Surgeline. i hope to find all the leaks and get them taken care of. will the dealer know what im talking about if i ask or will i need a part number?
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Old 06-21-2012, 05:45 PM   #25
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update. took it into Surgeline for the smoke test. no leaks, all was just fine with the air system, now i just need to do a compression test on the car. i plan on doing it myself. is there anyone in the portland oregon area that has done this? could use a hand.
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