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O2 readings on 89tbi

Discussion in 'The Garage' started by MudFlap, Oct 5, 2004.

  1. MudFlap

    MudFlap 1/2 ton status

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    I have an 89 tbi, with a couple of airflow mods and I am running headers with about 18" of pipe after each header. the O2 sensor is in the header collector and it is a one wire.

    I took some O2 reading last night and here is what I got

    Idle 0 to +.35 jumping around alot occasionally it would settle around +.5
    Cruise 0 to +.35 jumping around alot
    WOT +.66 to +.77, steady, it was lower at lower RPMs and higher at higher RPMs
    Decel -.22

    I am thinking that my O2 sensor is not heating up enough to read correctly unless it is WOT. I am going to get the vacuum fuel pressure regulator. But I am wondering if I should get a heated O2 sensor too. What do yall think?

    Thanks

    Trey
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    0-.35 sounds wrong to me. It will definitely bounce around as the mixture is adjusted, however, it shouldn't get to 0 unless the O2 sensor isn't working right. (either damaged or too cold)

    voltage vs. mix chart
     
  3. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    Yes it should jump around, thats the sensor switching rich to lean. It should be higher then .35, more closer to .7 or 800Mv. Its not that simple to just take out the 1 wire and put in a 3 wire. If you want to test the O2 you can do the propane enrichment test.
     
  4. MudFlap

    MudFlap 1/2 ton status

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    I thought that to wire in a 3-wire all you had to do was supply power to one wire, ground the other wire and the third wire is the signal. Is that wrong? My question is do I need one? Is it that why my readings jump around so much?

    Let me be a little more descriptive. At cruise speeds the reading go from around 0 to .15 to .07 to .35 to 0 to .20, etc. all in a matter of fractions of a second. The reading vary randomly and change very fast. My previous post might have been misleading, I am not saying that it cycles from 0 to .35 to 0 to .35.

    I am thinking that at partial throttle and cruise rpms (or idle) there is not enough heat to allow the O2 sensor to function properly, but under WOT there is enough heat to allow them to function properly that is why I get a constant reading under WOT.

    What do yall think?

    Thanks

    Trey
     
  5. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    The readings are supposed to jump around, if there not, then its not working. That means its switching rich lean, rich lean, and its supposed to do it quickly. Usually between 200 and 800 mV.
     
  6. fortcollinsram

    fortcollinsram 1/2 ton status

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    [ QUOTE ]
    I thought that to wire in a 3-wire all you had to do was supply power to one wire, ground the other wire and the third wire is the signal. Is that wrong?

    [/ QUOTE ]

    Installing a 3-wire is EASY. Just wire in a Ignition switched 12V+ for the heater power and then a Ground for the heater and the other wire is for the signal. I am putting a 4-wire in and it is the same way except it adds one more ground to ground the sensors signal through a good ground instead of the exhaust
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    All the problems I've heard of with the O2's going cold has been at idle.

    Not to say it can't be an issue, but the O2 sensor could be shot as well, instead of being cold.

    As was mentioned, the difference between rich and lean is EXTREMELY small, and changes much quicker than the scanner or winALDL will show. So the quick changes are not an issue, it's the ranges of millivolts that is an issue.
     
  8. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    [ QUOTE ]
    I am putting a 4-wire in and it is the same way except it adds one more ground to ground the sensors signal through a good ground instead of the exhaust

    [/ QUOTE ]

    Why not just put a 8 wire, like the new Porsches are going to have?!? /forums/images/graemlins/whistling.gif /forums/images/graemlins/smile.gif
     

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