What I assume is "limp mode" issue - Page 4
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This is a discussion on What I assume is "limp mode" issue within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Even the mechanics can't figure it out. I bought a demon car....

  1. #46
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    Even the mechanics can't figure it out. I bought a demon car.

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  3. #47
    Moderator Donkey's Avatar
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    Is the MAF installed the right way? Connector goes to the front of the car.
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  4. #48
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    Yes it is

    The shop is leaning toward map sensor now. They're seeing anywhere from 13 to 22 psi. I'm pretty sure 22 would do noticeable damage to a stock motor.

  5. #49
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    Yet another failed attempt. MAP sensor fixed varying boost readings but not the main issue.

  6. #50
    Registered User teflon_jones's Avatar
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    I'm struggling with how it can run perfectly with the MAF unplugged, but all screwed up once you plug it in. Since the MAF is good, that tells me it's the ECU that is not reading correctly what the MAF is sending it.

    Dumb question: Are all of the connections on the MAF plug good where they plug into both the MAF and the wiring harness? (Or maybe it doesn't plug into the harness and the wires from the plug on the MAF run all the way to where they terminate in the main harness, I can't remember.) Any of the wires clipped or frayed or otherwise worn, possibly grounding out?

    Could it be a bad 02 sensor feeding bad information back to the MAF, causing it to make inaccurate corrections to the air/fuel ratio?

    Maybe a bad EGR valve or some part of that system?
    Last edited by teflon_jones; 12-08-2010 at 02:32 PM.
    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

  7. #51
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    Quote Originally Posted by teflon_jones View Post
    I'm struggling with how it can run perfectly with the MAF unplugged, but all screwed up once you plug it in. Since the MAF is good, that tells me it's the ECU that is not reading correctly what the MAF is sending it.

    Dumb question: Are all of the connections on the MAF plug good where they plug into both the MAF and the wiring harness? (Or maybe it doesn't plug into the harness and the wires from the plug on the MAF run all the way to where they terminate in the main harness, I can't remember.) Any of the wires clipped or frayed or otherwise worn, possibly grounding out?

    Could it be a bad 02 sensor feeding bad information back to the MAF, causing it to make inaccurate corrections to the air/fuel ratio?

    Maybe a bad EGR valve or some part of that system?
    Just brought it home from the mechanic. Yeah the MAF wires look great. Changed the front O2 already. I'm completely out of ideas, I might have to just dump it at Subaru for a while since I've got way too much going on to rip it apart again.

    I think I'll make one more run through of hoses and wires tonight though. Maybe something is loose on/near the ECU I dunno.

    You guys rock for all the help though, I hope I can repay it someday.

    Anything I can log that would help?
    Last edited by Zarlan; 12-09-2010 at 08:07 AM.

  8. #52
    Registered User teflon_jones's Avatar
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    If you changed the front 02 already, then I'd look at the EGR system next. There's not too many things it could be other than this.
    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
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  9. #53
    Moderator Donkey's Avatar
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    Quote Originally Posted by teflon_jones View Post
    If you changed the front 02 already, then I'd look at the EGR system next.
    No USDM WRX or STI has an EGR system.
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  10. #54
    Registered User teflon_jones's Avatar
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    Quote Originally Posted by Donkey View Post
    No USDM WRX or STI has an EGR system.
    No? I thought they left that on there when they started bringing them to the US. My car is so far dismantled I can't look at it for reference any more.
    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

  11. #55
    Moderator Donkey's Avatar
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    OP-You need to flash back to the stock map if you have not and you more than likely have a post MAF leak.
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  12. #56
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    Quote Originally Posted by Donkey View Post
    OP-You need to flash back to the stock map if you have not and you more than likely have a post MAF leak.
    I have flashed back to the stock map. I've gone back and forth a few times just to be sure.

    Also, I checked for leaks 3 or 4 times and the shop had it for a week, they also checked, as did Subaru.

    With stage 1 the issue occurs ~3200 RPM, stock ~4500 RPM. MAF disconnected runs like it should.

    The dealership can't get to it for about 2 weeks so I'm trying to squeeze in some attempted fixing time between work and mom in the hospital. Not easy.

  13. #57
    Registered User teflon_jones's Avatar
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    Are you sure the other MAF you tried in it was the correct part number? Or that it wasn't broken?

    If all you're changing is whether the MAF is plugged in, then there's really just a few components that could be causing the issue:
    MAF - Bad sensor or wiring - See question above
    ECU - Bad ECU - possible
    02 - Bad sensor - Already replaced, so should be ok.
    Piping - Leak - Checked already, so should be ok.
    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

  14. #58
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    Quote Originally Posted by teflon_jones View Post
    Are you sure the other MAF you tried in it was the correct part number? Or that it wasn't broken?

    If all you're changing is whether the MAF is plugged in, then there's really just a few components that could be causing the issue:
    MAF - Bad sensor or wiring - See question above
    ECU - Bad ECU - possible
    02 - Bad sensor - Already replaced, so should be ok.
    Piping - Leak - Checked already, so should be ok.

    The new MAF was purchased directly from the dealership and is the correct part number. I'm going to follow all the wiring and inspect it when I get a chance.


    Hopefully that's the issue!

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  16. #60
    Good news, everyone! xxxxxxxAnub1s's Avatar
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    Your MAF appears to be working okay. Is it still acting funky?
    Cody
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    Good news, everyone!

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