Boost problem
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This is a discussion on Boost problem within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; got a 02 wrx check engine light came on. Stopped at my local auto zone they said it was bank ...

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    Boost problem

    got a 02 wrx check engine light came on. Stopped at my local auto zone they said it was bank 1 running lean so the said it was my 02 sensor ( befor the cat ) . Replaced it and now the boost psi will not go over .05 mpa . new 02 sensor is aftermarket bosh .Any help would be appreciated

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    Quote Originally Posted by btsplat View Post
    got a 02 wrx check engine light came on. Stopped at my local auto zone they said it was bank 1 running lean so the said it was my 02 sensor ( befor the cat ) .
    Did the CEL go off? If the CEL is still on, it probably wasn't the O2 sensor. The CEL you have described is probably PO171. The O2 sensor is among the possible causes but is not the most common.

    If the CEL is still on: Put the correct O2 sensor back on. Go to the store again and buy some CRC MAF cleaner and a new paper air filter. Replace the air filter, remove and carefully clean your MAF, and check for vacuum and boost leaks. Also check the reference connection to the fuel pressure regulator -- but do all that only after you've replaced the filter, made sure the top of the filter enclosure is on correctly and tight, and cleaned the MAF carefully but thoroughly. Then reset the ECU.

    Replaced it and now the boost psi will not go over .05 mpa . new 02 sensor is aftermarket bosh .Any help would be appreciated
    Did you disconnect something while fighting the O2 sensor? Check everything again just to be sure.
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    best way to check for vacuum leaks??

    Quote Originally Posted by SD_GR View Post
    Did the CEL go off? If the CEL is still on, it probably wasn't the O2 sensor. The CEL you have described is probably PO171. The O2 sensor is among the possible causes but is not the most common.

    If the CEL is still on: Put the correct O2 sensor back on. Go to the store again and buy some CRC MAF cleaner and a new paper air filter. Replace the air filter, remove and carefully clean your MAF, and check for vacuum and boost leaks. Also check the reference connection to the fuel pressure regulator -- but do all that only after you've replaced the filter, made sure the top of the filter enclosure is on correctly and tight, and cleaned the MAF carefully but thoroughly. Then reset the ECU.



    Did you disconnect something while fighting the O2 sensor? Check everything again just to be sure.

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    cel went off , changed air filter cleaned maf ,no change .on the way home cel came on had it scaned same code p0171 .this time they said the problem is the maf.what is the best way to check for vacuum leaks

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    Visually, closely and carefully. Soap water won't work for vacuum, only for boost. When you cleaned the MAF, did you spray into the cylinder itself (the housing; the sensor is buried in there) not just on the visible part?

    Check also the FPR connection, and all this assumes you have the correct factory intake and factory BPV.
    WRX Info Links, Courtesy TheJ
    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

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    I will check it this weekend. the car is stock . Do you recommend a cold air intake if so what brand,thanks for all the advice.

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    cel came back on today ,had it scanned same code po171 since i all ready replaced my upstream o2 sensor they said it was the mass air flow sensor.i could not find any vacuum leaks.after i get this problem stright i would like to install a cold air intake any recommendations .the car is stock ( 02 wrx ). thanks for any and all advice!!!

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    Quote Originally Posted by btsplat View Post
    cel came back on today ,had it scanned same code po171 since i all ready replaced my upstream o2 sensor they said it was the mass air flow sensor.i could not find any vacuum leaks.after i get this problem stright i would like to install a cold air intake any recommendations .the car is stock ( 02 wrx ). thanks for any and all advice!!!
    A cold air intake is one of the reasons the car would generate a PO171. After you figure out this problem, don't install a cold air intake.

    I've had PO171 and it was simple to fix -- I cleaned the actual MAF, not just the exterior, and replaced the air filter. If yours is coming back, read this thread:
    http://forums.nasioc.com/forums/showthread.php?t=475620
    then read that thread again, and start methodically troubleshooting. It can be a pain.
    Last edited by SD_GR; 05-15-2011 at 06:07 PM.
    WRX Info Links, Courtesy TheJ
    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

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    good info thanks. is your impreza stock. what is the best first mod ??? thanks again for all the help !!!!!!!!!!

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