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Thread: O2 sensors : 1 righ and 1 lean

  1. #1
    primerib is offline Cadillac Owners Member
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    O2 sensors : 1 righ and 1 lean

    Replaced the O2 sensors today. front sensor was grey/white which I believe it means lean, the rear one was black which appears to be rich. Any ideas what I should take a look at first to get these both back to normal.


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  3. #2
    Sevillian273's Avatar
    Sevillian273 is offline Cadillac Owners Connoisseur
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    Re: O2 sensors : 1 righ and 1 lean

    The difference in the two sensors could simply be caused by the resulting running condition of one of them failing. Could also be bad injector(s) on one bank or a really bad constant misfire... Check for code E046. How does the car run before/after the new 02 sensors?

  4. #3
    primerib is offline Cadillac Owners Member
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    Re: O2 sensors : 1 righ and 1 lean

    car runs okay. seems to be missing/lacking smoothness on acceleration. Kinda poor MPG. I'm betting it's a fuel delivery issue.

    how can I check the injectors in a '95 Deville 4.9L?

  5. #4
    primerib is offline Cadillac Owners Member
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    Re: O2 sensors : 1 righ and 1 lean

    okay, I'm grabbing a Noid Light set. I'll try the stethescope trick too

  6. #5
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    Re: O2 sensors : 1 righ and 1 lean

    A noid light will only tell you if the computer is sending a pulse to the injector. Aside from the stethoscope you can also apply voltage to the injector terminals(engine off of course) and listen.

  7. #6
    carnut is offline Cadillac Owners Master
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    Re: O2 sensors : 1 righ and 1 lean

    If you did not have a service engine now light on and a code related to weak, lazy oxy sensors, you now have 2 good spares. The color of the probe has nothing to do with how they operate. Monitored thru on board diagnostices you can watch the voltage change to verify switching lean/ rich at the right intervals.

  8. #7
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    Ranger is offline Cadillac Owners Member
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    Re: O2 sensors : 1 righ and 1 lean

    Quote Originally Posted by primerib View Post
    car runs okay. seems to be missing/lacking smoothness on acceleration. Kinda poor MPG. I'm betting it's a fuel delivery issue.

    how can I check the injectors in a '95 Deville 4.9L?
    Have you checked for a leaky FPR?

  9. #8
    primerib is offline Cadillac Owners Member
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    Re: O2 sensors : 1 righ and 1 lean

    yes, I checked the FPR. I pulled the vacuum hose, no leakage

  10. #9
    drewsdeville is offline Cadillac Owners Master
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    Re: O2 sensors : 1 righ and 1 lean

    Use your onboard diagnostics and check block learn and integrator values to determine actual fuel trim instead of guessing what the car is doing.

  11. #10
    primerib is offline Cadillac Owners Member
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    Re: O2 sensors : 1 righ and 1 lean

    okay, I've heard of this onboard diagnostic stuff, but how do you do it?
    haynes manual isn't cool enough to have that I guess

  12. #11
    primerib is offline Cadillac Owners Member
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    Re: O2 sensors : 1 righ and 1 lean

    oh wait, I found a section in the haynes manual about it. I'm reading now


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