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Causes of rich condition [3RZ] [Data inside]

Discussion in '1st Gen. Tacomas (1995-2004)' started by cmj, Oct 30, 2017.

  1. Oct 30, 2017 at 8:39 PM
    #1
    cmj

    cmj [OP] Well-Known Member

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    I've suspected that my 3rz has been running a bit rich for a while. Long story but I replaced my head twice in 3k miles. When I took the head off after 3k miles I was really surprised how much carbon buildup there was.

    I got a CAN data logger and watched the O2 voltage. I don't have the fuel trim channel for this dataset but based on my understanding of what a healthy system's O2 data looks like, I think something is not right with mine.

    Here is a plot under steady state highway driving, all warmed up:

    o2_sen_hwy.png

    As you can see, the dc bias is about 0.6V instead of 0.45V like it should be. The O2 sensor is a new Bosch 13104. The engine has new plugs, fuel filter, air filter, and a fresh valve job.

    Any ideas what to check?
     
  2. Oct 30, 2017 at 8:42 PM
    #2
    Bishop84

    Bishop84 Well-Known Member

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    EGR Valve, try to block it off with some tin from a spread out coke can and recheck readings.

    What I do is unbolt it to the manifold, take the gasket, trace it and simply reinstall a gasket without a hole for exhaust gasses to pass through.
     
  3. Oct 30, 2017 at 9:11 PM
    #3
    cmj

    cmj [OP] Well-Known Member

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    Hadn't considered EGR. I'll give it a try.
     
  4. Oct 31, 2017 at 12:55 AM
    #4
    Glamisman

    Glamisman Well-Known Member

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    how is/are the cats and the rest of the exhaust system?
     
    Dalandser likes this.
  5. Oct 31, 2017 at 1:01 AM
    #5
    INSAYN

    INSAYN Well-Known Member

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    Might need to clean or replace your MAF sensor.
     
  6. Oct 31, 2017 at 11:35 AM
    #6
    Bishop84

    Bishop84 Well-Known Member

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    Typically MAF issues are lean, unmetered/registering air getting past a sensor results in lean.
     
  7. Oct 31, 2017 at 2:40 PM
    #7
    DrZ

    DrZ Well-Known Member

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    I don't know why the EGR valve would cause a problem with the O2 readings. The exhaust gases are inert, CO2 and H2O, so they don't affect the fuel/air (O2) ratio at all.
     
  8. Oct 31, 2017 at 8:43 PM
    #8
    Clay_916

    Clay_916 Well-Known Member

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    O2 voltage looks fine. Why do you think it’s lean?
     

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