Lazy O2 sensor???

Discussion in 'Performance' started by kbuskill, Feb 13, 2019.

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  1. kbuskill

    kbuskill ***CAUTION*** I do my own stunts!

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    So here's the question...

    Do you guys think that this means I have a problem with the drivers side O2 sensor???
    rps20190213_124258_566.jpg

    When I turn off the truck with the OBD2 scanner still connected and Torque Pro app still running the Long Term fuel trims for bank 1 don't drop to zero like the others do.

    I'm really not certain what this means but I am thinking about changing the upstream O2 sensors on both sides just in case.

    What do you guys think???

    @swathdiver
     
  2. swathdiver

    swathdiver Full Access Member

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    I dunno, have to think about that some. I'll look into it tonight.
     
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  3. HiHoeSilver

    HiHoeSilver Away!

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    What does it look like live at idle?
     
  4. swathdiver

    swathdiver Full Access Member

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    Not really seeing anything. There was a mention of the numbers being stored in memory when the engine was shut off but key still on but no explanation as to why the other trims zeroed out.

    But if the O2 sensors are lazy, they will move slowly, erratically and not all the way through the range when they are graphed and are lazy. One of mine has gone lazy and I'll replace the pair of upstream sensors soon. It no longer rises up to the 900s but only to the 700s and then doesn't always go back down all the way or stays there too long.

    Trims are different with each fuel type and are best computer wise on E85 @ 72-80%. Motor's been running real good though on this E30.
     
  5. kbuskill

    kbuskill ***CAUTION*** I do my own stunts!

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    Well it's the LT trim that seems to be acting weird so live at idle doesn't really do much for LTFTs.
     
  6. HiHoeSilver

    HiHoeSilver Away!

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    I meant the O2 in question. Pretty easy to spot whether it's lazy or not by viewing the graph at idle. It'll either be switching from close to 0 up to about 900 and back every second(ish) or it won't.
     
  7. kbuskill

    kbuskill ***CAUTION*** I do my own stunts!

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    One other thing I noticed today that I find strange is that when I filled up the other day with 89 octane from a Mobil station the Ethanol % said 3.xxx%.

    I didn't think anything about it other than "wow, that's pretty low alcohol content".

    Then today after driving for 200 miles on that tank, all of a sudden out of no where, it changed to showing 17.xxx% ethanol.

    It was almost like it was stuck at a wrong reading and then finally figured it out.

    This again makes me highly suspicious of the O2 sensors since that would be where the ECM would get it's ethanol content reading from.

    I think I am going to just replace both of the up stream O2s and forget about it.
     
  8. HiHoeSilver

    HiHoeSilver Away!

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    Still curious to see the graph. Your ethanol content is determined by the Vitual Flex Fuel Sensor. I'm pretty sure there's more to it than the O2 data, but I had a hard time finding specifics. Mine got goofed somehow once, and had me throwing lean codes. I did learn you should not reset the content % unless the tank has regular gas in it. Also, when it recognizes a refueling event it needs to be driven a certain time or distance, otherwise it aborts the calculation.
     
    Last edited: Feb 14, 2019
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  9. kbuskill

    kbuskill ***CAUTION*** I do my own stunts!

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    I haven't watched it on a graph but I have the STFTs and LTFTs for both sides on my screen as you can see from the pic and the STFTs seem to bounce around just fine.
     
  10. swathdiver

    swathdiver Full Access Member

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    I've seen the alcohol content change before too during a tank of fuel. Not just within the first seven miles but many miles or days later, the computer is always checking and striving for peak performance.
     
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