trick the O2 sensor?

Discussion in 'Chevy Truck Forum' started by cstaehli, Aug 18, 2008.

  1. cstaehli

    cstaehli New Member

    Joined:
    Aug 18, 2008
    Messages:
    2
    Likes Received:
    0
    I have a '96 3500 crewcab with a 5.7L. I removed the catalytic convertors as they were plugged solid. My plan was to ensure that the convertors were the cause of the poor power I had been experiencing for ages. I immediately noticed a dramatic improvement and was quite happy, but by the next day I was having periods of heavy black smoke out the tailpipe with poor power and then a sudden change (ecm?) and the smoke would clear and I would launch off into the great power of the day before. I am wondering if it is caused by the o2 sensors now being confused (as you know there are 4 on this rig) or have I got another issue? Thanks for your time.
     
  2. stumpuller454

    stumpuller454 Well-Known Member

    Joined:
    Dec 26, 2007
    Messages:
    2,206
    Likes Received:
    62
    did this problem happen right after they were removed?
     
  3. stumpuller454

    stumpuller454 Well-Known Member

    Joined:
    Dec 26, 2007
    Messages:
    2,206
    Likes Received:
    62
    should throw a CEL without cheaters, you can get a custom tune that can cancel out the rear o2 signal too, i recommend that, its few bucks but you can get some more HP and fuell economy too...
     
  4. 75K30

    75K30 Senior Member

    Joined:
    Jul 19, 2006
    Messages:
    3,690
    Likes Received:
    168
    Welcome to the site:
    O2 sensors, are nothing more than a simple value that the ECM uses to calculate an air fuel mixture.
    O2 simulators can be made with simple resistors, or purchased. These can be used with stock ECM programs, as well as aftermarket programs.

    Yes, your problem sounds as though the ECM is going full fat without a decent O2 refrerance. It does not know closed loop from full loop, or how to manage either one right now.
     
  5. cstaehli

    cstaehli New Member

    Joined:
    Aug 18, 2008
    Messages:
    2
    Likes Received:
    0
    Thank you for your replies - I will look further into this - in the meantime, if I was to unplug the rear 2 sensors, would it run better than now - rather than confusing the ecm, will it just run in a default mode instead?
     
  6. z07

    z07 Senior Member

    Joined:
    Feb 12, 2008
    Messages:
    391
    Likes Received:
    27
    It could also be that the reason the old cats were "plugged solid" is that the O2 sensors are liars.

    Cats don't just one day decide to clog up. There was a rich condition problem before the cats were removed that caused the cats to die and the same condition is still there.

    A shop with an exhaust gas analyzer and data logger should be able to see in real time what the exhaust gas looks like and what the O2 sensors are reporting.
     
  7. stumpuller454

    stumpuller454 Well-Known Member

    Joined:
    Dec 26, 2007
    Messages:
    2,206
    Likes Received:
    62
    unpluggin the sensors with throw the CEL, truck will run in open loop continuous, not gonna get great mileage, kinda like it would be runnin in limp mode
     
  8. stelmadl

    stelmadl Senior Member

    Joined:
    Nov 11, 2005
    Messages:
    116
    Likes Received:
    5
    not sure about the smoke issue, but because your cats aren't doing the job/ missing, the computer is compensating for it. there are o2 sensor simulators (to replace the current o2 sensors) you can buy.....to trick the computer that there's a cat present. removing the cat, or course, is illegal. i used to own a camaro, and some forum owners thought removing the cat would give some noticable horsepower....but to avoid the codes, simulators had to be installed.
     

Share This Page