Rough idle and random engine stalls help plz
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This is a discussion on Rough idle and random engine stalls help plz within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; So I have a 2003 wrx 5spd with 131k and since I for it I've noticed it idles strange. Now ...

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    Registered User kawiman6565's Avatar
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    Rough idle and random engine stalls help plz

    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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    Registered User teflon_jones's Avatar
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    Any mods on the car? Maintenance history including plugs, timing belt, air filter, etc?
    Scott
    Past Subies - '11 STI Limited stage 1+ and '04 STi stage 2+
    '13 Wrangler Rubicon - custom front bumper w/12k lb winch & off-road lights, skid plates, diff guards, etc.
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    Registered User kawiman6565's Avatar
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    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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    Registered User kawiman6565's Avatar
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    Oh, and a 12.5lbs flywheel

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    Moderator Donkey's Avatar
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    Clean the IAC valve.
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    Registered User kawiman6565's Avatar
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    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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    Registered User kawiman6565's Avatar
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    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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    Registered User kawiman6565's Avatar
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    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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    Registered User kawiman6565's Avatar
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    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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    Registered User teflon_jones's Avatar
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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.
    Scott
    Past Subies - '11 STI Limited stage 1+ and '04 STi stage 2+
    '13 Wrangler Rubicon - custom front bumper w/12k lb winch & off-road lights, skid plates, diff guards, etc.
    '04 Porsche 911 Turbo GT2 clone 600 HP/TQ
    '77 F-150 heavily modded for off-roading

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    Moderator T0rque's Avatar
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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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    Moderator T0rque's Avatar
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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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    Registered User teflon_jones's Avatar
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    ^^^ What Borque said.....
    Scott
    Past Subies - '11 STI Limited stage 1+ and '04 STi stage 2+
    '13 Wrangler Rubicon - custom front bumper w/12k lb winch & off-road lights, skid plates, diff guards, etc.
    '04 Porsche 911 Turbo GT2 clone 600 HP/TQ
    '77 F-150 heavily modded for off-roading

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    Registered User kawiman6565's Avatar
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    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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    Moderator T0rque's Avatar
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    IACVs do some funky **** when bad..


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