02 wrx post maf hose replacement and wild boost swing
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This is a discussion on 02 wrx post maf hose replacement and wild boost swing within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; so this morning i get my replacement post maf hose, a mishimoto(matches my timc hoses), and replace it at lunch ...

  1. #1
    Registered User tirerob's Avatar
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    02 wrx post maf hose replacement and wild boost swing

    so this morning i get my replacement post maf hose, a mishimoto(matches my timc hoses), and replace it at lunch with a minimum amount of fuss. little bit of trimming but i already knew they came a bit long to accommodate cai intake systems. installed, new hose clamps and a quick seal check and ecm reset. drove back to work and all is good. no quick reset though as i was running a bit late.

    tonight on the way home though. i hit the highway with intent of making the ecu happy. oh yea...happy all right. turbo? Not Happy. boost fluctuating at mid to full throttle. basically anything past wastegate pressure and the needle is a swinging. then the boost spike hit, thankfully as i had my eye on the gauge. spiked to 15-16psi and then dropped. further attempts at mid to full throttle(rpm or gear didnt make much difference but i never went past 5500rpm)resulted in the same behavior. spike to 15-16 psi then drop to 10-11psi and hold. maybe a little wiggle. and my foot would come right off the gas too.

    up until todays after maf hose install and ecm reset my boost has been a absolute rock at 14.5 psi. never spiked, never dropped. definitely never went over factory boost levels. nothing else has been changed and i am still untuned. currently, all the plastic hoses have been replaced. timic, turbo inlet, and post maf are all now after market. the afta-maf was changed out for two reasons. ugly. uuugly. and, it was worn really thin in one of the bellow creases. swapped to illuminate unmetered air. ive checked all the vacuum lines and the lines for my boost gauge too. gauge aside, i can actually hear the turbo boost spike and drop when the gauge does its dance.

    post maf hose the straw that broke my ecm's learning curve? i didnt think(with as much as ive already replaced) that it would cause that much chaos but i am about to remove it to wrap up the old plastic piece in duct tape and reinstall untill i get it figured out. thanks n stuff in advance guys n gals.
    when my friends come up, i hear, "you sold the camarrrroooh.....HOLY BLEEP A WRX!"
    Ya has that effect on me too.
    Rob

    Where did he go?? http://www.clubwrx.net/forums/builds...ll-thread.html

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    Master Baiter EJ257's Avatar
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    Blind guess...

    You had a post-MAF intake tract leak. Now that it's fixed with the new hose, you're in a classic WGDC/TD boost oscillation situation (too much boost, reduce WGDC, too little boost, add WGDC, repeat). That's obviously without seeing any kind of a datalog, but based on your description, that's my first thought.

    Do you have the ability to datalog?
    2005 WRX STi (Mods | Virtual Dyno)

    Resident Tuner @ WTF Tuning

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

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    Registered User tirerob's Avatar
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    thanks ej. no logging just yet. still fighting romraider to computer talkie problems. that sounds just about like what my needle was doing. it would boost, drop, boost again(almost as high) then settle down at too low for target. it seemed to bounce more the longer i held it at .75 throttle to wide open. the needle bounced just a bit faster than i can work the throttle but is definitely right petal dependent. before i replace the stock after maf hose im going back to check and see if i didnt crack open a vacuum line or cause a leak by over tightening the new hose clamps. i might even reset the ecu again and reload the vinchu reset procedure. or something similar. just weird.... but that hose did fit really tight and i had to do a bit of twisting to get it in. who knows.
    when my friends come up, i hear, "you sold the camarrrroooh.....HOLY BLEEP A WRX!"
    Ya has that effect on me too.
    Rob

    Where did he go?? http://www.clubwrx.net/forums/builds...ll-thread.html

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    Quote Originally Posted by EJ257 View Post
    Blind guess...

    You had a post-MAF intake tract leak. Now that it's fixed with the new hose, you're in a classic WGDC/TD boost oscillation situation (too much boost, reduce WGDC, too little boost, add WGDC, repeat). That's obviously without seeing any kind of a datalog, but based on your description, that's my first thought.

    Do you have the ability to datalog?


    This.. There is no way a post maf hose would cause this unless there was a leak or a problem already existing..

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    Registered User tirerob's Avatar
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    Quote Originally Posted by Dat8687 View Post
    This.. There is no way a post maf hose would cause this unless there was a leak or a problem already existing..

    this is what i thought too. Only my car....fix the problem and its compounded by three others. currently checking everything vacuum related again anyway and brushing up on ecu reset procedures. i might have caused a problem when i did it this morning. wish i had a tester, its going to be all visual atm darnit
    when my friends come up, i hear, "you sold the camarrrroooh.....HOLY BLEEP A WRX!"
    Ya has that effect on me too.
    Rob

    Where did he go?? http://www.clubwrx.net/forums/builds...ll-thread.html

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    Quote Originally Posted by tirerob View Post
    this is what i thought too. Only my car....fix the problem and its compounded by three others. currently checking everything vacuum related again anyway and brushing up on ecu reset procedures. i might have caused a problem when i did it this morning. wish i had a tester, its going to be all visual atm darnit
    Did you break the vacuum line from the inlet to the turbo/boost control? Check this line if its leaking slowly it can possibly allow a boost spike.. Because its like a manual boost controller and will bleed off boost so the sensor wont recognize the actual boost and it might overboost..

    Sorry for that long run on . Like running a Tee between the solenoid and the wastegate.. And bleeding it off into the air.. It will cause a higher boost level without throwing a code often.

    And I'm not saying that's what happened to you but check it.

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    Master Baiter EJ257's Avatar
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    Quote Originally Posted by tirerob
    this is what i thought too. Only my car....fix the problem and its compounded by three others. currently checking everything vacuum related again anyway and brushing up on ecu reset procedures. i might have caused a problem when i did it this morning. wish i had a tester, its going to be all visual atm darnit
    Visual inspection isn't suitable. You need to either pressure/smoke test the vehicle to know if there are leaks.
    2005 WRX STi (Mods | Virtual Dyno)

    Resident Tuner @ WTF Tuning

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

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    Registered User tirerob's Avatar
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    well nothing appears to be damaged, bent out of shape, bad, but i am zip tying a few connections and replacing some vacuum hose that feels hard.going to check the connections at the ebcs to just to make sure. this must have been a problem well before replacing the afta-maf but what stumps me is it Never showed. i was all proud n stuff lol of my solid factory boost levels hahahahah
    when my friends come up, i hear, "you sold the camarrrroooh.....HOLY BLEEP A WRX!"
    Ya has that effect on me too.
    Rob

    Where did he go?? http://www.clubwrx.net/forums/builds...ll-thread.html

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    Registered User tirerob's Avatar
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    Quote Originally Posted by EJ257 View Post
    Visual inspection isn't suitable. You need to either pressure/smoke test the vehicle to know if there are leaks.
    +1 n stuff. lol, working with what i have for now. never needed to build a pressure tester cause no problems right? course....now the hardware store are closed haha!
    when my friends come up, i hear, "you sold the camarrrroooh.....HOLY BLEEP A WRX!"
    Ya has that effect on me too.
    Rob

    Where did he go?? http://www.clubwrx.net/forums/builds...ll-thread.html

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    Registered User tirerob's Avatar
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    well now. ebcs vacuum lines are hard a rocks and spin freely. replace.......


    edit. ANNNNNDDDD waahlah. checking the rest of the lines the thin vacuum line from the bottom of the stock bcs snapped in my fingers not a inch from the t fitting at the boost pill/waste gate split. hello then!
    when my friends come up, i hear, "you sold the camarrrroooh.....HOLY BLEEP A WRX!"
    Ya has that effect on me too.
    Rob

    Where did he go?? http://www.clubwrx.net/forums/builds...ll-thread.html

  12. #11
    Registered User tirerob's Avatar
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    OK after replacing the vacuum lines to and from the ebcs I seem to have the over boosting under control. Needle still swings about three to five psi at wot under 5000. I suspect my boost gauge fitting might be broke but would that be a problem spot all the way at the bov line? More driving for ecu happy and a fresh tank of gas. Back to the road!
    when my friends come up, i hear, "you sold the camarrrroooh.....HOLY BLEEP A WRX!"
    Ya has that effect on me too.
    Rob

    Where did he go?? http://www.clubwrx.net/forums/builds...ll-thread.html

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