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  1. #1
    Active Member One Ring slvrultrasport's Avatar
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    Mar 15 2017
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    Summerville, SC

    Angry B6 s4 lean condition....

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    Hello everyone, long time vw owner and audi owner. New here though. I'm have a little bit of an issue with my b6 s4. I've searched and searched the forums and cant find anything with an issue quite like mine.

    Having a reoccurring cel related to bank 2 lean condition. (P0174 I believe) everytime I clear it, it comes back after a short drive. No loss of power with these codes. Usually triggered with a wot pull or two. (Obviously after relearning fuel trims after code clear) that code is intermittently paired with a bank one lean code as well. But is far more inconsistent. I also have the typical catalyst efficiency codes related to my catless downpipes but they usually dont pop a cel. I've watched MAF values and logged them using obd13 and the values were just out of spec, so I replaced the MAF with a known good one i had in the garage. Cleaned that one with MAF sensor cleaner. After searching the forums and finding that most of you gurus have seen other issues related to the lean condition codes, I jumped into trying to diagnose without throwing a bunch of new parts at it. Checked and retorqued the intake manifold bolts, every single one was extremely loose. Checked all the vacuum lines (that are able to be seen without putting it into service mode) found the line that runs from the intake manifold flapper to the y at the back of the intake broken. Replaced the whole brittle plastic line.

    After all three of these fixes, everything appeared good again. No cel, no codes. Did plenty of wot pulls just to test, logged MAF values and watched partial and idle fuel percentages. Put about 150 miles on the car with no issue and no light. Started the car up this last night, CEL again! pulled codes and found the same bank 2 lean code. I'm basically at a loss here trying to find out why this car is saying it's running lean. I only use 93 and have run seafoam through the fuel. I dont want to start throwing parts at it so if anyone could help try to diagnose this further I'm all ears! Let me know if there is any other info you need. Thanks everyone for reading this book of a post!
    Dolphin grey B6 s4; coilivers, billyboat downpipes, resonated cat back, rs4? Sway bar, full led bulb swap, jhm short shifter, apr tune, drop in k&n

  2. #2
    Active Member One Ring slvrultrasport's Avatar
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    395557
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    Summerville, SC

    Here is a screenshot of my current mixture adaptations.



    https://drive.google.com/file/d/1-S9...w?usp=drivesdk
    Dolphin grey B6 s4; coilivers, billyboat downpipes, resonated cat back, rs4? Sway bar, full led bulb swap, jhm short shifter, apr tune, drop in k&n

  3. #3
    Active Member One Ring slvrultrasport's Avatar
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    Mar 15 2017
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    395557
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    Summerville, SC

    Hopefully this way to upload works. Current adaptations again. Screenshot_20181107-060228_OBDeleven.jpeg

    Sent from my SM-G955U using Audizine mobile app
    Dolphin grey B6 s4; coilivers, billyboat downpipes, resonated cat back, rs4? Sway bar, full led bulb swap, jhm short shifter, apr tune, drop in k&n

  4. #4
    Veteran Member Four Rings q_dubz's Avatar
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    Dec 16 2008
    AZ Member #
    36417
    My Garage
    Single Turbo V8 S4
    Location
    EAST COAST

    hmmm, try this, swap the front o2 sensors. Possible the sensor is bad.

  5. #5
    Active Member One Ring slvrultrasport's Avatar
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    Quote Originally Posted by q_dubz View Post
    hmmm, try this, swap the front o2 sensors. Possible the sensor is bad.
    I'll try that this evening. But with the issue of the intermittent bank one lean code, messing with the 02 sensors could possibly cause the bank one sensor to fail. No?

    Sent from my SM-G955U using Audizine mobile app
    Dolphin grey B6 s4; coilivers, billyboat downpipes, resonated cat back, rs4? Sway bar, full led bulb swap, jhm short shifter, apr tune, drop in k&n

  6. #6
    Veteran Member Four Rings q_dubz's Avatar
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    Dec 16 2008
    AZ Member #
    36417
    My Garage
    Single Turbo V8 S4
    Location
    EAST COAST

    Quote Originally Posted by slvrultrasport View Post
    I'll try that this evening. But with the issue of the intermittent bank one lean code, messing with the 02 sensors could possibly cause the bank one sensor to fail. No?

    Sent from my SM-G955U using Audizine mobile app
    Swapping wont hurt. Your fuel trims show bank 2 to be major the culprit. Swap and see if the code moves. If it doesn't, you possibly have an exhaust leak right at the flange. ;)

  7. #7
    Veteran Member Three Rings
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    Aug 09 2012
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    If possible can you show the readings of the front lambda and rear oxygen sensors as well. Iirc the rear oxygen sensors can also manipulate fuel trim data by causing the system to run rich or lean depending on if it is stuck. I had that happen to me on a Volvo before.

  8. #8
    Active Member One Ring slvrultrasport's Avatar
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    This one was at idle at operating temp. Screenshot_20181107-154639_OBDeleven.jpeg

    Sent from my SM-G955U using Audizine mobile app
    Dolphin grey B6 s4; coilivers, billyboat downpipes, resonated cat back, rs4? Sway bar, full led bulb swap, jhm short shifter, apr tune, drop in k&n

  9. #9
    Active Member One Ring slvrultrasport's Avatar
    Join Date
    Mar 15 2017
    AZ Member #
    395557
    Location
    Summerville, SC

    Dolphin grey B6 s4; coilivers, billyboat downpipes, resonated cat back, rs4? Sway bar, full led bulb swap, jhm short shifter, apr tune, drop in k&n

  10. #10
    Active Member One Ring slvrultrasport's Avatar
    Join Date
    Mar 15 2017
    AZ Member #
    395557
    Location
    Summerville, SC

    Dolphin grey B6 s4; coilivers, billyboat downpipes, resonated cat back, rs4? Sway bar, full led bulb swap, jhm short shifter, apr tune, drop in k&n

  11. #11
    Active Member One Ring slvrultrasport's Avatar
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    Mar 15 2017
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    Summerville, SC

    The 78ohm for both upstream sensors freaked me out a little bit. Until I noticed both are showing 78ohm. Far off from the downstream, but none the less, still high resistance imo.

    Sent from my SM-G955U using Audizine mobile app
    Dolphin grey B6 s4; coilivers, billyboat downpipes, resonated cat back, rs4? Sway bar, full led bulb swap, jhm short shifter, apr tune, drop in k&n

  12. #12
    Active Member One Ring slvrultrasport's Avatar
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    Mar 15 2017
    AZ Member #
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    Location
    Summerville, SC

    Any other input from you guys? Going to be swapping the 02 sensors tonight but trying to see if there is anything else I should mess with while I'm in there.

    Sent from my SM-G955U using Audizine mobile app
    Dolphin grey B6 s4; coilivers, billyboat downpipes, resonated cat back, rs4? Sway bar, full led bulb swap, jhm short shifter, apr tune, drop in k&n

  13. #13
    Veteran Member Four Rings q_dubz's Avatar
    Join Date
    Dec 16 2008
    AZ Member #
    36417
    My Garage
    Single Turbo V8 S4
    Location
    EAST COAST

    Nope

  14. #14
    Veteran Member Three Rings
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    Aug 09 2012
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    Quote Originally Posted by slvrultrasport View Post
    Any other input from you guys? Going to be swapping the 02 sensors tonight but trying to see if there is anything else I should mess with while I'm in there.

    Sent from my SM-G955U using Audizine mobile app
    Just as Q said. Swap the front O2 sensors first. Keep an eye out for any exhaust leaks in the area that can introduce excess oxygen around or before the sensor itself (usually followed by dark soot marks around the leak area). If that doesn't change anything, reinstall them back to original position and swap the rear oxygen sensors.

  15. #15
    Active Member One Ring slvrultrasport's Avatar
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    Mar 15 2017
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    For any still interested in this issue, I fixed the car this past weekend. There was a pretty big exhaust leak at the downpipe to manifold connection. Replaced with all new hardware. Code is gone and all seems well again! Adaptations are all within spec again.

    Sent from my SM-G955U using Audizine mobile app
    Dolphin grey B6 s4; coilivers, billyboat downpipes, resonated cat back, rs4? Sway bar, full led bulb swap, jhm short shifter, apr tune, drop in k&n

  16. #16
    Veteran Member Four Rings q_dubz's Avatar
    Join Date
    Dec 16 2008
    AZ Member #
    36417
    My Garage
    Single Turbo V8 S4
    Location
    EAST COAST

    Hey, i win!

  17. #17
    Veteran Member Three Rings
    Join Date
    Aug 09 2012
    AZ Member #
    98417
    Location
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    Quote Originally Posted by q_dubz View Post
    Hey, i win!
    OP wins as well, problem solved. Good stuff.



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