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O2 Sensor Problems 308 QV

Discussion in 'Technical Q&A' started by Dr Tommy Cosgrove, Aug 8, 2007.

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  1. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
    Owner Rossa Subscribed

    May 4, 2001
    36,599
    Birmingham, AL
    Full Name:
    Tommy
    #1 Dr Tommy Cosgrove, Aug 8, 2007
    Believe it or not I have now come full circle with this O2 thing. I bought the car 10 years ago with it disconnected and I never bothered to hook it back up until now but I have always wondered why someone would bother to do that, especially in a state that had emission checking (in this case GA).
    After I installed a new one, now I know... Surges

    My engine surges driving down the road and it drove me crazy. It ran smooth, but it was as if I was tapping the brake pedel with my left foot every few moments. I disconnected it and things are back to "normal" again. I realize this is probably just a CO adjustment issue but that is another problem with my car. There is no place to sample pre-cat exhaust on my car since I had the little sample pipes removed and welded on the front bank when they rusted thru and started leaking about 5 years ago. Back then sampling fresh exhaust gas was not a problem because I didn't have a cat and all I had to do was snake up the tailpipe.

    If I can't figure out a solution, the spotted owl, rain forests, the ozone layer, and Al Gore can all just kiss my butt because I'm gonna leave it disconnected...

    Any suggestions? Would it be easier to simply reinstall my test pipe, adjust it and reinstall my Hyperflow when I'm done?

    (wouldn't that be funny - a test pipe actually being used as a test pipe?)
     
  2. Badman

    Badman Formula 3

    Mar 4, 2007
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    Bruce Wayne
    #2 Badman, Aug 8, 2007
    Geez, first the A/C now the O2 sensor... you've just got it out for those cute little owls ;)

    You can use the duty cycle input to the frequency valve to tune the fuel mixture. With the oxygen sensor disconnected, the input to the FV should be 50%. This just checks that everything else is basically ok. Then with the oxygen sensor connected, it should cycle back and forth from about 45% - 55%. If the swing is higher or lower than that, you can adjust the mixture at the fuel distributor to bring it in line. If you don't have a duty cycle meter, a dwell meter will work but you've got to do the conversion. The Probst book on the k-jet system has the conversion numbers I think, and is a good book to have for this kind of stuff. After you've tuned the mixture, you can then check the exhaust gas post-cat just to make sure there's nothing wildly wrong.
     
  3. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
    Owner Rossa Subscribed

    May 4, 2001
    36,599
    Birmingham, AL
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    Tommy
    #3 Dr Tommy Cosgrove, Aug 8, 2007
    We tried adjusting the CO with an ohm meter between the sensor and the ecu. There HAS to be an easier way than that. Watching the meter bounce between .9 and .1 volts while adj the CO screw just isn't the way to do this. I totally believe the BEST way is simply to sniff the exhaust directly instead of trying to adjust it by reading other instruments downstream in the car translating it for me. Things can get lost in translations as we all know. With my car, by the time I am reading it somewhere else it's just a rumor.

    I have access to one of those big old Sun Machines that reads CO but at this point I don't know where to stick the probe (no jokes please :)
     
  4. Badman

    Badman Formula 3

    Mar 4, 2007
    1,116
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    Bruce Wayne
    #4 Badman, Aug 8, 2007
    Yes, you're right, that is the best way if you can get to the exhaust pre-cat. But you'll still want to check the FV duty cycle even if you did adjust the mixture with an EGA, to make sure the O2 sensor and ECU are all cooperating correctly to produce the correct input to the CIS.
     
  5. No Doubt

    No Doubt Seven Time F1 World Champ

    May 21, 2005
    72,740
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    Mr. Sideways
    #5 No Doubt, Aug 8, 2007
    I've got the Innovate LM1 sniffer. You're welcome to use it to get things set up right on your car.


    For 348's, a surging throttle is almost always a bad O2 sensor (though sometimes it's air entering the exhaust in front of the O2 sensor). For your 308, I just don't know.
     
  6. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    May 4, 2001
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    #6 Dr Tommy Cosgrove, Aug 8, 2007
    My O2 sensor is brand new Bosch right out of the box. How big is that machine? I may borrow it and just reinstall my test pipe to set it.
     
  7. No Doubt

    No Doubt Seven Time F1 World Champ

    May 21, 2005
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    Mr. Sideways
    #7 No Doubt, Aug 8, 2007
    You don't have to do any of that. The LM1 sensor just screws into the OEM O2 sensor bung.
     
  8. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
    Owner Rossa Subscribed

    May 4, 2001
    36,599
    Birmingham, AL
    Full Name:
    Tommy
    #8 Dr Tommy Cosgrove, Aug 8, 2007
    When can I come get it??
     
  9. No Doubt

    No Doubt Seven Time F1 World Champ

    May 21, 2005
    72,740
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    Full Name:
    Mr. Sideways
    #9 No Doubt, Aug 8, 2007

    Come by this afternoon when you close shop.
     
  10. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
    Owner Rossa Subscribed

    May 4, 2001
    36,599
    Birmingham, AL
    Full Name:
    Tommy
    #10 Dr Tommy Cosgrove, Aug 8, 2007
    PM me your cell # again, I can't find it around here. Must be at home.
     

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