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Thread: Drivers O2 sensor erratic? 2 bar SD 5.3 Turbo

  1. #1
    Tuner in Training
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    Sep 2013
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    Drivers O2 sensor erratic? 2 bar SD 5.3 Turbo

    Gents - Details of setup are below. Current tune and log are attached. I am trying to get the idle and PT dialed in close on narrowbands alone. Drivers O2 goes nuts. ** I have checked for exhaust leaks, I have swapped O2's from side to side, I have pulled plugs. The behavior stays consistent on drivers side regardless of sensor change. Appreciate review of my tune and log, and any guidance.

    5.3
    LJMS turbo cam
    S475 turbo
    Boost ref FPR set at 58psi base
    65lb Deatschwerks injectors (Closer to 75 @ 58psi)
    4L85E
    Circle D converter
    Attached Files Attached Files

  2. #2
    Possibly a vacuum leak or misfire? Use a flammable spray and check everywhere while watching for short term fuel trim to go negative.

    Before it even gets to closed loop bank 1 is spiking lean while bank 2 is solid at 960 mv. When you get into boost(which your map is not showing correctly?) during that WOT run bank 1 actually went more rich than bank 2.

  3. #3
    Advanced Tuner
    Join Date
    Apr 2017
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    Meridian MS
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    529
    Is the left O2 reading the other bank's flow as well? Or are the banks separate until the turbo inlet?

  4. #4
    Tuner in Training
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    Sep 2013
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    Thanks for input - Cannot find any vacuum leaks. I changed my boost control pressure connections - O2 issue remains the same.

    Each exhaust bank stays separate until the turbo, and its a divided T6 flange/turbo. I do have the wastegate plumbed and welded into the turbine housing itself - if that could matter.

    My O2 sensors are NOT Equi-distance from the manifolds. passenger side (right) is approx 3-4in from the manifold, and the drivers (left) O2 is approx 1.5 feet from the manifold. When we built the exhaust setup, I was told distance did not matter on O2's. But I cant help but think this is causing the issues.

    Is there any way to compensate for the different distances of the O2's in the tune?

  5. #5
    Tuner in Training
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    Oct 2018
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    It's very weird because the behaviour looks exactly like an exhaust leak. Driver's bank has big fuel addition with the passenger bank being pretty good. How are you checking for exhaust leaks? Could you post a photo of the drivers side? How far is o2 turbo outlet?

  6. #6

  7. #7
    Tuner in Training
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    Sep 2013
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    I realize these are not great photos - Simply showing the distance between manifold and sensor from side to side. On checking for exhaust leaks - albeit silly, I have been putting my hand near all joints and even holding a kleenex nears joints. I cant find, hear, or feel anything?

  8. #8
    Try using an automotive stethoscope but just use the open hose end that is connected to your ears to listen.

  9. #9
    Tuner in Training
    Join Date
    Oct 2018
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    35
    I would definitely check the flex joint and look for a blown out 3 bolt gasket if you are using graphite gaskets. You can use dawn dish soap and water. You can try using the blower function of a shop vac to blow air into the downpipe to create pressure, I've done that before with good success. Might need a few rag to place around the blower to seal the end better. Obviously don't do this with a dirty hose. A leaf blower would work too. Just stating my experiences, I hope it helps.