WOT Engine Problem
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This is a discussion on WOT Engine Problem within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Having a little problem with my 2004 WRX. Mods are: Invidia catless DP TurboXS Up pipe Cobb Intake Cobb Stage ...

  1. #1
    Registered User Killerkanadian's Avatar
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    WOT Engine Problem

    Having a little problem with my 2004 WRX.

    Mods are:
    Invidia catless DP
    TurboXS Up pipe
    Cobb Intake
    Cobb Stage 2 AP flash

    Holding off on my larger intercooler until i get this thing figured out.

    WOT in First, and usually second gear are fine. Once I get into 3rd-5th gears, WOT the power seems to teeter. Feels like it boosts up, then the power cuts, then it boosts up again. Maybe back and forth every couple seconds.

    My my only guess is that it has something to do with either thinking its over boosting or a fuel problem. When i bought the car a couple months ago it had a MBC, and it caused it to overboost and throw codes. Currently it's not throwing codes. When it was overboosting the cars power would cut out big time, then come back to feeling normal. The previous owner thought it was just Turbo Lag .

    Any how, no where close I can get an immediate pro tune. I'm thinking if i drop the Cobb AP and get a tune it would probably fix any problems. Since that's not an immediate option, any suggestions on what might be the problem? Also, im not real fresh on the AP but I could data log anything that might help figure the situation out.

    Thanks gents and ladies.

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  3. #2
    Master Baiter EJ257's Avatar
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    Likely a boost oscillation. Datalog your boost parameters (WGDC, target boost, MRP) and post it to Google Docs.
    2005 WRX STi (Mods | Virtual Dyno)

    Resident Tuner @ WTF Tuning, LLC

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    Registered User Killerkanadian's Avatar
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    Wasn't sure what MRP was. Didn't see anything on there that was MRP. Tried to google it, and thought it might be manifold pressure. If I need to log something else I'd be glad to do it again.

    Here's what I got though.

    https://docs.google.com/spreadsheet/...VRDNEdLeV85WUE
    Last edited by Killerkanadian; 05-21-2012 at 07:06 PM.

  5. #4
    Master Baiter EJ257's Avatar
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    MRP = Manifold Relative Pressure

    You should not be hitting 21.XX PSI on a StageII tune.
    2005 WRX STi (Mods | Virtual Dyno)

    Resident Tuner @ WTF Tuning, LLC

    "Never trust anything that bleeds for a week and lives ..."

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  6. #5
    Registered User Killerkanadian's Avatar
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    Probably not great on my 91 octane Oklahoma gas either.

    Any idea what I should look into for this problem?

  7. #6
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    Try turning down the boost on the MBC to 18 Psi or so... Or put the OEM boost control back on, or, buy the 3port boost control COBB just came out with...
    '02 WRX 4EAT, 311,000KMs/194,500Miles, Sold. Best car I ever had. '09 STi stage 1, hope this one will be good too...

  8. #7
    Registered User Killerkanadian's Avatar
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    I got tired of messing with the MBC, and got tired of it throwing the engine off so I took it off and ran the lines to the stock boost seleniod. I was thinking about the grimmspeed or a cobb, but if it requires anything other than plug and play, then I'm not really sure about it. Unfortunetly if i ever want anyone to ever work on the car that knows what they're doing, ill be driving 1 1/2 hours to OKC.

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    Registered User Killerkanadian's Avatar
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    Flashed the stage 2 91 octane LWG onto the car. I think it runs a little better but I can't say for sure. It seems to stumble up around 4,500 RPM every time in second gear. Tomorrow I can take another log if anyone would look at it for me.

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    Registered User Killerkanadian's Avatar
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    2 Things that I feel might have something to do with this issue, I hadn't thought of.

    1, I think it might need new spark plugs. Totally on a hunch, I have no idea what plugs are in there.
    2, I have an aftermarket Vacuum line restrictor pill which i bought from autozone when I took off the MBC.

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    Quote Originally Posted by Killerkanadian View Post
    2 Things that I feel might have something to do with this issue, I hadn't thought of.

    1, I think it might need new spark plugs. Totally on a hunch, I have no idea what plugs are in there.
    2, I have an aftermarket Vacuum line restrictor pill which i bought from autozone when I took off the MBC.
    I'd go with the restrictor pill... Get A bigger ID one, JMO
    '02 WRX 4EAT, 311,000KMs/194,500Miles, Sold. Best car I ever had. '09 STi stage 1, hope this one will be good too...

  12. #11
    Registered User teflon_jones's Avatar
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    Your first post lists out your mods, then later you say it has a MBC but don't list that in your mods list. The Cobb stage 2 tune isn't designed to work with a MBC. They have very specific map notes on what's supported.

    Can you list out everything that's different on your car from a stock car?
    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

  13. #12
    Registered User Killerkanadian's Avatar
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    No, I said the car came with a MBC. I took it off and it's sitting in my garage. There was no restrictor pill, so i replaced it with a little plastic one I bought at Autozone.

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    Registered User Killerkanadian's Avatar
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    So i put my MBC back onto the car, and now since I had the Cobb AP I could play with it until i got the boost into it's sweet spot. Got it to run great at 17.0 PSI and I'm not messing with it from there.

    Thanks for helping me trouble shoot it guys.

  15. #14
    Moderator Donkey's Avatar
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    You still need to get the car professional tuned. I would not run an MBC on that car with the Cobb OTS map. This has been documented over and over. There is a reason Cobb states what mods you can run with their maps. An MBC is not one of them. Part Throttle/Full Boost will make your engine go "pop" if it's running those maps due to the car running to lean.
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  16. #15
    Registered User Killerkanadian's Avatar
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    Well here's the thing. I don't have the stock resistrictor pill which comes with the car. If anyone could link me to where you can buy it (i believe it only sells with the whole vacuum line assembly), I would appreciate that because I would rather be using that set up. However since I don't have that set up, my low tech MBC is basically doing the job of the missing restrictor pill. It's not one of the fancy ones that cause the car to spool up early or anything like that.

    That's just my logic anyhow. I know it's wrong according to Cobb, but I'm not seeing how it would cause my car to run lean. If I am wrong I would gladly listen to why my I am incorrect.

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