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Thread: O2 reading lean issues...

  1. #1
    Tuner in Training
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    O2 reading lean issues...

    Hey guys... working on my gen3 5.3 . Having an issue with bank 2 reading lean. My wideband is also in bank 2 and follows what the narrow band is saying. I've pulled all the injectors and cleaned/flowed them. Swapped them side to side while doing it. Changed plugs, moved coil packs side to side, moved O2 sensors side to side, fixed any possible exhaust leaks that i could find pre O2. At my wits end.... running out of time before Sick Summer to get this car right. Any thoughts? Car was doing fine... one day just started running lean... and it shows its on bank 2. I turned closed loop back on today and even though its showing lean, its got negative fuel trims....which confuses me. Short idle log and tune attached...
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  2. #2
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    ok....found a few messed up parameters in the o2 section of the tune for closed loop and got those corrected, but still basically the same. After logging another vehicle and looking at it, I think I'm barking up the wrong tree (to a point). I think the larger issue is bank one not having much oscillation. So its actually running very rich. Everything I've done has included both sides, so still nothing has changed with any of my changes. I'll dig into the regulator and make sure its not plugged on the drivers side maybe? New log attached with some driving...
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  3. #3
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    Have you tried swapping O2's left to right?

  4. #4
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    I have. No change.

  5. #5
    Tuning Addict blindsquirrel's Avatar
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    Why is Bank 1 stuck rich all the time, not switching? Do B1/B2 go to ~450mV when unplugged?

  6. #6
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    It is weird it Bank 1 switches a little bit after awhile? Like it isnt getting enough heat like a bad O2. Id put it in open loop through the scanner and see what it feels/sounds like to rule out corrections.

    Do B1/B2 go to ~450mV when unplugged?
    This^

    Seems like you might have the connecters switched.

  7. #7
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    I'll have to check and see what it says when unplugged. I'm sure they are not switched... this car has been up and running since 2021. Just put a new engine combo in this year. Looked at old logs from last year and all was well with the world as far as o2 goes. O2 has been swapped left to right with no change, so I've ruled out o2 sensors. I need to check the v-band on the drivers side and make sure there isn't a leak I can't hear... but I would assume that would show lean and not rich. And yes...occasionally it will start switching which is odd. I'll also make sure no wires got pinched during the install. 99.99 percent sure that they are all fine, but I will verify

  8. #8
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    Forgot to reply about putting it in open loop. It's been running strictly in open loop up until today when I turned closed loop back on just to see what it did with the fuel trims. Same behavior.

  9. #9
    Tuning Addict blindsquirrel's Avatar
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    Sensors are probably nuked from running stupid open loop for so long.

  10. #10
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    o2's both go to .448v when unplugged. I verified bank 1 and 2 by unplugging each individually so I'm sure they are correct. May upload and old tune with the current injector info to help rule out a tune issue. Not sure that could be possible to affect only one bank, but worth a try? I'm leaning towards something wrong with the return line going to the regulator on that bank maybe. I'll check that in the morning when its not a fire hazard.
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  11. #11
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    I'm down with changing the sensors... can't hurt. But the readings should have swapped from bank one to bank two and visa versa when i swapped the sensors and they didn't. And its been in open loop for probably a total of MAYBE 100 miles. Had closed loop turned off for tuning so it wasn't making it's own adjustments yet.

  12. #12
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    Well fellas.... after cleaning out the regulator, resealing the vband on bank 1 and swapping o2 sensors again... no change. I modified my tune from last year to work with the new injectors and MAP and now its reading fine. Evidently it is somehow in the tune. I'll work on this tune and get it to play well with the new engine combo and see how it goes. Guess that's what I get for starting with someone else's tune for a base...
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  13. #13
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    Fixed

    Fixed it. The tune i was building off of had the injector bank select set to all 1's. Setting it back to the correct 1's and 0's has fixed the problem. Thanks for being a sounding board! Now i can get somewhere!
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  14. #14
    Tuning Addict blindsquirrel's Avatar
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    I really should have caught that... being that it looked like only one half of a bank-swapped situation.