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Thread: Lean with Missfire's

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    Basic Member Mason Johnson's Avatar

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    Lean with Missfire's

    Hello, I have a 2004 wrx that currently has a missfire on all 4 cylinders along with a lean code. I don't have the codes atm but will add them to the post later. Wanted to see some possible suggestions as to what could be wrong. Thanks!


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    Tinkerer Eagleye's Avatar

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    Re: Lean with Missfire's

    Does the car have any modifications, if so what? Did you buy the car with mods or do them during your ownership? Is there an aftermarket tune on the car currently? Are you running an Accessport or Open Source program to see any data other than the codes?

    15 GBP STi

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    Basic Member Mason Johnson's Avatar

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    Re: Lean with Missfire's

    The only modifications that are on the car that I'm aware of as I just got the car last Monday is an intake and a turbo back exhaust. Car is on a stage 2 tune on 93 with a COBB AP. The tune is also a COBB tune. I'd like to say AFR is a little high at idle. Floats around 18-20 but I also don't know if that's good or bad. First turbo subaru trying to learn the car as I progress. Car idle's at 500-600rpms. And before you ask, I didn't pay a lot for the car so I'm not to worried about what could be on that's aftermarket. To me the car looks bone stock other than the above modifications. Car is pushing 15 PSI. Invidia down pipe with HKS catback exhaust.


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    Tinkerer Eagleye's Avatar

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    Re: Lean with Missfire's

    Several issues are jumping out given wheat you are saying.
    1. Off the shelf Stage 2 Cobb Tune on those mods is not going to be good. The Cobb map is designed for use with Cobb's Intake and Downpipe. Other models use differing designs that can greatly change fueling requirements.
    2. 18-20 AFR is way high. 14.5-15 is where you should see it floating at idle. Down around 11 at WOT IIRC.
    3. Saying you aren't worried about what is on it aftermarket is a bit strange to me. I would want to know what is on a car I am buying so I know if anything needs to be checked out with the tune prior to getting into boost. It may also tell you what could be going on.

    With all that said I would check the usual stuff: look for boost/vacuum leaks, exhaust leaks, pull a spark plug, and reflash the map. Beyond that I would log a couple of pulls and post the info on here. There are of course other things to look at but I wouldn't get too carried away until you check for leaks and reflash.

    15 GBP STi

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    Eats rice, drinks V8. Batmobile_Engage's Avatar

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    Re: Lean with Missfire's

    Before you do anything else, carefully remove and clean (with an aerosol MAF cleaner) your MAF. If it's not reading properly, we'll never figure this out. It's probably fine, but it's something we should try to rule out of the equation early on.

    Sometimes, idle AFR measurements aren't very accurate. But if your AFR reporting is still off, when on throttle, I would be concerned. Otherwise, I agree with the above; 14.5ish at idle, 11ish at WOT.

    What intake is on the car? I'd be willing to bet that is the primary culprit in this problem.

    Quote Originally Posted by IGOTASTi View Post
    I will put the last drop of oil on Earth in my turbocharged machine and smile amongst the carcinogenic fumes as I burn T-Rex’s family tree just so I can pass you, sideways in the middle of a blizzard.
    Member Journal: https://www.igotasti.com/vBforum/showthread.php?5453-The-Batmobile_Engage-Member-Journal

  7. Top Of Page | #6
    Tinkerer Eagleye's Avatar

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    Re: Lean with Missfire's

    Quote Originally Posted by Batmobile_Engage View Post
    Before you do anything else, carefully remove and clean (with an aerosol MAF cleaner) your MAF. If it's not reading properly, we'll never figure this out. It's probably fine, but it's something we should try to rule out of the equation early on.

    Sometimes, idle AFR measurements aren't very accurate. But if your AFR reporting is still off, when on throttle, I would be concerned. Otherwise, I agree with the above; 14.5ish at idle, 11ish at WOT.

    What intake is on the car? I'd be willing to bet that is the primary culprit in this problem.
    Agreed

    15 GBP STi

  8. Top Of Page | #7
    Basic Member Mason Johnson's Avatar

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    Re: Lean with Missfire's

    Reason I'm not to worried is the car has 226k miles on the car. The intake is a K & N Typhoon intake system. Now that I know it makes sense. Is there any other type of off the shelf tunes I can use or do I need to just go to a base map tune and then get a protune?


  9. Top Of Page | #8
    Basic Member Mason Johnson's Avatar

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    Re: Lean with Missfire's

    Should I use a stage 1 map as it doesn't require a COBB turbo back. Or should I just run a base map due to the K & N intake? Car has a stock turbo so I'm assuming it's a normal waste gate. Car has no other modifications from what I can tell.


  10. Top Of Page | #9
    Eats rice, drinks V8. Batmobile_Engage's Avatar

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    Re: Lean with Missfire's

    If you're running a Cobb OTS tune with those mods, I'd probably run one of the Stage II tunes. Heck, maybe even one of the low(er) boost, 91 octane tunes. Then of course, fill it with 93 for safety's sake until you can get it protuned on a dyno.

    At 226k miles, anything could be wrong, but if I had to bet I would say that the tune is does not take into consideration that intake. Thus, the MAF is not scaled properly to accurately read the increase in air and you end up running too lean.

    Quote Originally Posted by IGOTASTi View Post
    I will put the last drop of oil on Earth in my turbocharged machine and smile amongst the carcinogenic fumes as I burn T-Rex’s family tree just so I can pass you, sideways in the middle of a blizzard.
    Member Journal: https://www.igotasti.com/vBforum/showthread.php?5453-The-Batmobile_Engage-Member-Journal

  11. Top Of Page | #10
    Basic Member Mason Johnson's Avatar

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    Re: Lean with Missfire's

    So should I put on the stage 2 tune and data log then and see what happens? I'm assuming the only way to fix the issue is to get the cobb intake system.


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