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Thread: Erratic Narrowband Function?

  1. #1
    Fuel Injected!
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    Jan 2018
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    41

    Erratic Narrowband Function?

    Hoping someone can give me some clarity on this log. My suspicion is that I have a sensor issue, although I'm not sure exactly sure. $0D L31 swap with carb manifold and throttle body adapter.

    To give some background, my old narrowband bit the dust about 3 months ago and I replaced it with a unit from Standard Motor products (SG241). I knew the old sensor was bad because the computer would never enter closed loop. After I installed the new sensor, I can now enter closed loop, however the signal from the narrowband is extremely erratic most of the time. In this log, there are brief periods where the narrowband and wideband follow similar patterns, but for the most part the NB is cycling between a high point and essentially zero volts.

    Known issues, first and foremost the spray pattern of my injectors is not great. I rebuilt the throttle body when I swapped the engine two years ago and apparently didn't do a great job as it has the TBI drip and the truck surges slightly with just mild throttle application. Think I am going to just swap the injectors and try some oring lube on the injectors when I rebuild as I have heard that has good results. Is it possible this is the behavior I am seeing while driving?

    Second, I was recently burned a plug wire. I have sense changed plugs and rectified that issue and the misfire is gone. Is it possible I could've fouled the sensor that quickly? It was not driven more than a mile or two with the misfire.

    Lastly I recently had some of my engine grounds break and had to replace them. This has been rectified with new ground straps. Is it possible that the sensor destroyed itself through lack of ground?

    If anyone has seen sensor behavior like this before and found a solution your knowledge would be greatly appreciated as this currently has me stumped.
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  2. #2
    LT1 specialist steveo's Avatar
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    Aug 2013
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    4,008
    In this log, there are brief periods where the narrowband and wideband follow similar patterns, but for the most part the NB is cycling between a high point and essentially zero volts.
    this is what a good o2 sensor pattern looks like (although i haven't seen your log)

    there's a reason they call them narrow bands. the band is actually too narrow for the injection system to attain, so what it does is get to the point where it's switching back and forth from rich to lean very quickly. that indicates the point where it's as close as possible to a stoich average.

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