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Thread: LS swapped S10 lean maxing out o2 sensor

  1. #1
    Lifetime Member mvvette97's Avatar
    Join Date
    Jul 2007

    Default LS swapped S10 lean maxing out o2 sensor

    Hi guys have a problem with running extremely lean. I got the 6.0 put back in the s10 due to pulling the heads and putting new lifters in. I was logging the idle and it started climbing in the trims to a point where it maxed out the drivers side and passenger side was not far behind. I thought the intake gaskets were leaking since I reused them so put a new set on and the same.I tried unhooking both o2 sensors to see what it would do Monitoring it with an installed stand alone wideband and it was reading 19 afr. It was actually running not bad. Any idea what could cause this? It was fine before. I did find on the shorty headers it was leaking at the header gasket and also down on the 3 bolt collector pretty bad. The O2 sensors are down stream of the leaks as well as the wideband sensor. Could the exhaust leaks of messed with the o2s making it go positive on the trims? If so I'm guessing it would mess with the wideband as well since they are both down about 8 inches from the leaks.Could it be not really lean and just being fooled to think it is from the leaks? Thats the only thing I can come up with.
    Last edited by mvvette97; December 3rd, 2022 at 02:36 PM. Reason: spelling

  2. #2
    Senior Member
    Join Date
    Dec 2016


    Exhaust leaks are bad. It will usually induce oxygen into the exhaust and tell the sensors you are falsely lean.

  3. #3
    Lifetime Member mvvette97's Avatar
    Join Date
    Jul 2007


    that's what I was kinda thinking as well since I wasn't able to find any vacuum leaks at all. Hopefull that's all it is because I don't know what else it could be because it was fine before I pulled the heads and cam. Had a guy mention maybe it's something with the cam but I really don't think so. I have done many cam swaps and never seen any of them do this.

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