Running Lean? Help! I didn't do anything...lately...
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This is a discussion on Running Lean? Help! I didn't do anything...lately... within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; modifications I have done to my car (2003 WRX): -silencer delete. left the end that got cut open. -3" S*RS ...

  1. #1
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    Running Lean? Help! I didn't do anything...lately...

    modifications I have done to my car (2003 WRX):

    -silencer delete. left the end that got cut open.

    -3" S*RS CatBack exhaust. From cat all the way into the engine bay is stock, downpipe uppipe all that.

    -dash replaced with LED lights.

    -18" rims

    -emblem repaint and de-badged.

    however irrelevant they are all listed.
    today check engine light came on and I got codes pulled at Autozone. Reads as follows:

    Fuel Level sensor circuit low input
    Probable cause:
    1 open or short circuit condition
    2 poor electrical connection
    3 faulty fuel level sensor

    &

    System too lean- bank 1
    probable cause:
    1 faulty MAF sensor
    2 large vacuum leak
    3 low fuel pressure
    4 plugged injector or cylinder misfire

    1st one caused by low wattage LED bulb in dash for fuel level ?
    it came up before and then shut itself off. this time the second code popped up though.

    2nd code I thought was because I didn't seal up the new exhaust very well, I cracked one bolt. But I used 4 gaskets and misc. hardware to get it down to almost no leakage. would that explain the large vacuum leak? my mechanic buddy says that it wouldn't be that because it is after the MAF sensors in the stock cat. is the exhaust enough to spool the turbo earlier and cause it to run lean?

    I'm not super savvy with cars but I'm learning and I don't understand why this would happen now, all those modifications have been the same for 3 weeks now, no further mods.

    Please help, thank you and sorry for the lengthy (but thorough!) post and my lack of proper grammar and punctuation.

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  3. #2
    He simply abides. SD_GR's Avatar
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    Quote Originally Posted by taWRX1990 View Post

    System too lean- bank 1
    probable cause:
    1 faulty MAF sensor
    2 large vacuum leak
    3 low fuel pressure
    4 plugged injector or cylinder misfire
    ...
    2nd code I thought was because I didn't seal up the new exhaust very well, I cracked one bolt. But I used 4 gaskets and misc. hardware to get it down to almost no leakage. would that explain the large vacuum leak?
    You don't know you have a vacuum leak. The CEL may indicate you do, but you don't know that yet.

    my mechanic buddy says that it wouldn't be that because it is after the MAF sensors in the stock cat.
    There is only one MAF sensor, no more, and it is not in the stock cat.

    is the exhaust enough to spool the turbo earlier and cause it to run lean?
    I do not understand what this means.

    I'm not super savvy with cars but I'm learning and I don't understand why this would happen now, all those modifications have been the same for 3 weeks now, no further mods.
    It can happen, that's not unusual.

    Tell your mechanic friend to check the intake and make sure there are no leaks, and that the filter is clean.

    Clean the MAF with a dedicated MAF cleaning product. Do not use a harsh chemical. CRC is one supplier of an appropriate product.

    Check for vacuum leaks anywhere in the intake path, the boost reference path, and for boost leaks in the boost path. Start at the intake and follow the black tubing.

    Check the reference tubing connection for the fuel pressure regulator.

    Check the tubing from the bypass valve on the intercooler.

    Make sure everything is connected. Usually a PO171 on a stock car is a dirty MAF, potentially because the air filter is junk, is dirty, is both junk and dirty, or the casing isn't sealed properly.
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  4. #3
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    I solved everything a much easier way.
    Totaled the car today. bye.
    And I am suppose to drive 36 hours away for my freshman year at Sierra Nevada College in 7 days....

    the location of MAF sensor and stuff would be my bad.

    just to kinda clarify form what I understand changing the entire exhaust including downpipe to a bigger diameter can create less back pressure and allow the turbo to spool to some extent faster and cause the lean condition. im just curious if that is correct?

    I duck-tapped the spot of the silencer delete and reset the computer by removing the negative terminal.
    the light didnt come on today as I delivered pizzas.

    But it's totaled it is all irrelevant. If it's not totaled I guess the insurance will cover it, and I'll sell it cause my premium is going to sky rocket and I cannot afford it. And every one checks car fax so if i can sell it, it probably wont sell for what its worth even if its better condition than pre-accident.

    FML FML FML FML FML

    P.S. one other note is I actually had the black intake tubing taken off during an auto-x event I ran my car in. It was sucking air, through the y-joint that the silencer was sawed off, straight into the air box. never had any check engine light that day and it was then put back on. only saying this cause it possibly eliminates an intake leak? not trying to be condescending I know that I don't know **** about cars beyond changing brakes, oil, and basic bolt on parts.
    Last edited by taWRX1990; 07-29-2009 at 08:58 PM.

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