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Discussion Starter #1
So I have a 2003 wrx 5spd with 131k and since I for it I've noticed it idles strange. Now I understand, from reading other threads and posts, that once at operating temperature I should idle at 750 rpm +/- 100 and mine does not. It idles fine wen cold but once it reaches this temp it dips to 500 rpms and fluctuates from 300 to 700 rpms and it's becoming common for this car to just randomly stall wen idling at a light for a prolonged period of time. I'm told this could be a vacuum leak or a faulty IAC valve but would like some opinions in the matter. Thank you for the help in advance. (I apologize if I'm incorrect with any of this, kind if a newbie to the scoobie)
 

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Any mods on the car? Maintenance history including plugs, timing belt, air filter, etc?
 

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Discussion Starter #3
It has a dual core radiator, stage 2 clutch, catback exhaust, and HKS BOV so not any major mods to it and the timing belt and water pump kit should be arriving at my house any day now and I'm putting plugs in this week. I have few service records from previous owner so I'm playing "catchup" with the maintenance since I just got the car recently
 

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Discussion Starter #6
Great thank you, I'll try this tomorrow. I tried to search for a DYI or a how to on this and didn't see one, not sure if I just missed it or if there isnt one so of someone could post a link or so a brief walk through for it that would be greatly appreciated.
 

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Discussion Starter #7
Scratch that I was able to find a thorough DIY thank you for the help and I'll let you guys know if that clears up the problem
 

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Discussion Starter #8
So today I took the IACV off and poured gasoline into it and let it sit to loosen all of the buildup in it, it was very dirty, and then used q-tips to get all of it off/ out. I used them on ht part of the throttle body I could access from taking off the IAC. The buildup of blow by oil and what ever else was in there must have been the problem since my car now idles flawlessly. Thank you very much for the help guys!
 

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Discussion Starter #9
My car ran fine format of today and then went to absolute crap. It stalls at almost every stop and has a ton of hesitation in almost every gear. This only happened after I cleaned the IAC Car also threw a code for system rich. Any insight as to what this may be??
 

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A LWFW can cause idle issues, as can the BOV. But first thing to look at is the code of the car running rich. What specific code is it? There's a lot of different codes and just saying it's running rich doesn't help. The fact you don't know the mileage on the plugs is also a big red flag. Have you pulled any of the plugs to examine them?

A vacuum leak by itself shouldn't cause the car to run so rough and stall in any driving situation. Normally a vacuum leak will just cause it to have issues when it starts to build boost. Normally though, not all the time. The condition of the plugs and most importantly the code are what's needed next.
 

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CELs come on and leave a random number like a p0 type code, we need that code to assist you. Just cleaning a IACV doesnt necessarily fix the issue if the iacv is bad.. It leads me to believe that if your car ran great after cleaning it that the IACV may be bad and need replaced.. But that is just a shot in the dark since I dont have a code to go off of.
 

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When you took the IACV off did you disconnect the battery and let the system re-learn itself? Typically you want to let a car idle for a good 10 minutes after disconnecting the battery, without any other electrical items going so the car can re-learn a/f, ratios, idle all that stuff..
 

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^^^ What Borque said.....
 

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Discussion Starter #14
The cel went away while u was driving so I can't get the p0 number from it unless it pops back up. I haven't ha the car long and am yet to pull the plugs but I'm going to do so in the morning. Yes inhad the battery unplugged for about 20 mins or so and let the car idle for about 15 after putting the IAC back on and reconnecting the plug and battery. The car now has massive hesitation and periodically bucks when I'm building boost. It also hesitated more than it ever has and the CEL began to flash so I pulled overt read the code but it wasn't flashing or showing a CEL. I'm now lead to think, and am told, that this may be a coil pack that's on it's way out.
 

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Discussion Starter #16
I went out and started my car this morning and let it warm up And then took it for a spin. It felt perfectly fine today but still am putting new plugs in once my tools are back at my house. I'm hoping the IACV isn't bad seeing how expensive it is...
 

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Discussion Starter #19
So after swappig out the old plugs, previous owner clearly did not care about maintenance seeing how they were the stock plugs with 130k on them, the car runs like a top. The only catch is that it still idles a bit rough at times. When I took off the IACV to clean it I noticed that the throttle body was just as dirty as it was, would you recommend taking the TB off and thoroughly cleaning it and possible clear up this rough idle. It only idles rough when it is warmed up and it sits at around 500rpms +/- 50 and drops down to as low as 250 rpms and jumps back up. It is not vigorous and when it does do this it only happens every ten seconds or so. No CELs are currently present and I'm oping it will stU that way. My apologies for the late response but I've been crazy busy, thank you for all the help!
 

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I figured the plugs were a problem.

What about other items such as the air filter? I'd go through and do a basic maintenance check on everything. Also clean your MAF and run a few bottles of fuel system cleaner through it.
 
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