Engine Power Loss Under Boost
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This is a discussion on Engine Power Loss Under Boost within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Ive done an extensive amount of searching and have not found a similar problem. My 04 wrx missfires under boost ...

  1. #1
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    Inconsistant Missfire Under Boost

    Ive done an extensive amount of searching and have not found a similar problem.

    My 04 wrx missfires under boost in all gears, problem worsens in 2nd and 3rd gear. Cel like says missfire on #4. Prolem seems to lessen after motor has ran for an extended time. I feels like the rev limiter hits at 4-5k rpm.

    Put new plugs in. cleaned MAF. Took out intercooler and refitted all turbo and intake hoses. New fuel filter. cleaned the sock on the fuel pump. Tripple checked vacum hoses. Put some good octane boost in. new full tank of gas. cleaned air filter.

    Car turned 45k mi.
    No BOV, factory flywheel.
    Sti fuelpump and injectors.
    Upgraded intercooler
    vf54 turbo. Catless up/down pipe
    perrin Intake, exhaust.
    Protune on turbox's ecu.
    Boosting around 18psi.
    Just put in ngk platnium's 6. wanted one colder 7 but had no patience to order.


    I feel like I have covered alot of bases and still the problem worsens. My brain hurts and i have been scouring the area for a sutibale cliff to drive the car off of, need help.
    Last edited by Natedawg191; 05-12-2008 at 05:44 PM. Reason: More accurate

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    So i took it to my buddies tune shop. Seems to have stumpted them all. the code now reads Missfire on 2 and 4. Oddly that is the left bank.

    Cel light came on during idle and stayed on all the way to work 30miles. Engine did the same boost problem.

    Cleared the cel. No problems all the way home. Seemed almost fine underboost. although I got taken by a honda so something is still terribly ary. Tommorow morn I will look forward to the same cut out problem....

    Any idea would help.. this one is worth 10 points.

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    the thought did cross my mind. just doesn't seem plausable that 2 would go out at the same time. and such low milage... Ill try when i get off work..


    Anyone ever have a blown intake gasket???

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    Quote Originally Posted by Natedawg191 View Post
    the thought did cross my mind. just doesn't seem plausable that 2 would go out at the same time. and such low milage... Ill try when i get off work..


    Anyone ever have a blown intake gasket???
    You think a blown intake gasket is more likely than a blown coilpack?

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    I could see both being possible. I dont mean to discredit your theory. Im just basing the intake thought on a: excessive, or more than stock intake pressure. b: both 4 and 2 are on the same bank.

    Unfortunatly it is pouring out and I don't have to garage space to check the coilpacks tonight. (has to be the drivers side too). If that were the case is there an upgraded coil pack?? like a msd sort of thing?

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    Quote Originally Posted by Natedawg191 View Post
    I could see both being possible. I dont mean to discredit your theory. Im just basing the intake thought on a: excessive, or more than stock intake pressure. b: both 4 and 2 are on the same bank.

    Unfortunatly it is pouring out and I don't have to garage space to check the coilpacks tonight. (has to be the drivers side too). If that were the case is there an upgraded coil pack?? like a msd sort of thing?
    Kinda, but it's not worth the money. You could buy these new fangled "plasma" coil packs that say they give a better spark, but that being said nobody has really put them through the grinder so to speak to prove their reliability versus OEM. I would just pick up a new/lightly used set if I needed new ones.

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    The coil pack is a very good idea. The new #2 cylinder miss could be a false reading because of the normal #4 problem. Id get the 7 plugs for sure. Deffinately swap the coil packs to see if the miss goes to the swapped cylinder. Id also swap the maf sensor from one of my friends wrx just to see if thats a possible problem. Also could be o2 sensors.


    Lead Wrench @ WTF Tuning, LLC

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    what are those new plugs gapped to?

    does the problem get worse as boost and rpms go up?

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    Registered User Timdog1650's Avatar
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    Quote Originally Posted by ride5000 View Post
    what are those new plugs gapped to?

    does the problem get worse as boost and rpms go up?
    That's a good point....improperly gapped plugs are going to cause all kinds of misses at higher RPM if they're too wide.

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    plugs gapped at .30 or .030 whichever. I know I need the 7's. The car had iradiums in it i replaced with a infuriour plug.... shame on me... point being that the plugs i put it had no significant effect whatsoever.

    I would like to tell you it gets worse under more boost but to be honest its pretty bad just at 4 - 4.5k. I usually chicken out and dont push it anyfurther. This isn't a little squeek or rattle. Its pretty bad. This problem has been getting progressivly worse over the last few months.


    I should also mention that the engine temp plays a huge factor in this... no i dont hop in my car in the morn and take off. I generously warm my car up. this problem seems to take place **unless** I have been out for a while like more than half hour of typical city/highway runtime. I feel it takes place untill the motors components have reached a peak metal temp. and even then. poor girl has lost her muscle.

    Also to mention I put in a BOV thinking that my factory BPV silonoid was defective.. I soon realized I had a new set of problems to deal with... This is how irrational my thinking can be sometimes... btw... $$BOV 4 SALE$$ hardly used...like **new**.. put new gaskets in and resealed the oem BPV back in.

    otherwise I feel it takes place untill the motors components have reached a peak metal temp. and even then. poor girl has lost her muscle.
    Last edited by Natedawg191; 05-14-2008 at 08:17 PM.

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    Quote Originally Posted by Natedawg191 View Post
    plugs gapped at .30 or .030 whichever.
    did you gap them yourself, or check the gaps yourself?

    never assume gaps are set right out of the box.

    I know I need the 7's. The car had iradiums in it i replaced with a infuriour plug.... shame on me... point being that the plugs i put it had no significant effect whatsoever.
    how do you figure it's an inferior plug? the heat range has nothing to do with what's happening right now.

    your car is misfiring. it happens only when you're starting to get on it and the boost is coming up.

    as cylinder pressures go up the energy required to create a spark goes up. marginal electrical system problems will suddenly become much worse with more boost and more rpm.

    I would like to tell you it gets worse under more boost but to be honest its pretty bad just at 4 - 4.5k. I usually chicken out and dont push it anyfurther. This isn't a little squeek or rattle. Its pretty bad. This problem has been getting progressivly worse over the last few months.
    how long ago did those plugs go in?

    when you swapped plugs did you remove the coilpacks from the harnesses? if so, double check the electrical connectors from the harness to each of the coils. they have small tabs that lock them into place on the coilpack that can become broken, and then the harness is only held in place by friction.

    get an obd2 scanner and pull some codes. if the misfires are as bad as you say they are there will be stored DTCs which will help point to the root of the issue.

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    Gapped the plugs myself. My infuriur plugs i didn't mention that it had iradiums and i put in platnium.

    Coil pack plugs looked it order when i did this 1 week ago.

    Not sure what an obd2 scanner is. I pretty sure that is what my friend used to pull a missfire code for both 3 and 2 cylinders.

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    swap the misfiring coils with the coils that don't miss. reset ecu. test drive. when misfires recur, scan for DTCs. if the misses changed cylinders then you've got coil issues. if they stayed the same then you've got mechanical and or ecu/electrical issues.

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    Swapped coilpacks all aroung and cannot isolate one single or two bad coilpacks... had 3 different missfires in one week w/o any swap. Tripple checked all electrical connections. double checked intake lines... put in one step colder iradium plugs.. (car was tuned with those in it) got plenty of gas through it. cleaned maf. new fuel filter.


    help help help... this is driving me nutz. i could bring back to tuner but im sure itll hurt the wallet for an idunno. besides my good friend is a tunner another tune shop whom also has no clue. (kinda like going to the doctor with a cold). I have alot of mods that were all put in before a protune. everything ran great for 30k miles... wtf.

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