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Thread: Commanded AFR going out of spec

  1. #1
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    Default Commanded AFR going out of spec

    Hello Guys,

    I am having an issue where all of the sudden the commanded AFR will go from the 14.68 Closed loop into "open loop" and 15.69 or 13.59 AFR.

    I have set all my open loop afr tables to 14.68 but I am still seeing those changes under unknown conditions...

    I have seen this on 2 cars... The first one I didn't pay much attention and the second one... Well... it's time to chack...I have tried pretty much everything... It appears to be a random thing...

    It will keep the last used STFT and LTFT and command a leaner 15.69 and/or a richer 13.59 on normal cruising... if you punch it, it will drop to PE normally... but still...

    COT is OFF

    Any ideas?

    Thanks
    "All that is needed for the triumph of evil is that good men do nothing..."

  2. #2
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    Anyone?
    "All that is needed for the triumph of evil is that good men do nothing..."

  3. #3
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    i'll try to find some info on it today but i've been told it's for emisions and something to do with "storing oxygen in the cats"?

  4. #4
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    hm... so this is totally intended... Ross.. any way to get rid of this??? it will sometimes get the car a bit unstable to drive... If you are cruising its a bit ok... but... if you are stop and go it simply gets the car to hesitate a tad. This is a cammed car of course.
    "All that is needed for the triumph of evil is that good men do nothing..."

  5. #5
    Lifetime Member GMPX's Avatar
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    I don't know what it is. Not something anyone else has complained of.
    I seem to recall the LS1 did something similar when it thought the O2 sensors weren't responding, it would richen things up in an attempt to see a response from the O2's, maybe this is along similar lines.
    I no longer monitor the forum, please either post your question or create a support ticket.

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    Well... thinking on that... since it first went leaner and then richer, I tried adjusting b1513 and b1514 to no effect as the car wouldn't go into closed loop. I tried inputing 1000 and 100 to see if it solved the issue and as I said, car wouldn't go into closed loop.

    I had seen this with road dataloggin on another vehicle and didn't pay much attention. But now this one again... another LS7... So... I'll keep investigating... i'll try logging HO2S1/2 v and see if there is a pattern.
    "All that is needed for the triumph of evil is that good men do nothing..."

  7. #7
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    i didnt have time today to find documentation on this but my car does this regularly whilst cruising.
    notice how the fuel trims even flatline while it commands 15.96 then 13.36
    i definitely think its intended.


  8. #8
    Lifetime Member GAMEOVER's Avatar
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    This is very interesting....
    2008 2WD Ext.Cab Silverado 1500 6.0 V-MAX E38(L76) & T42(4L70E) MAF Only CL Corvette Servo AFE CAI INNOVATIVE LM-2 WBO2

    FLASHSCAN V2 & AUTOCAL

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    You see ROSS!!! I am not inventing this

    Thing is... that I am sure that once the fuel trims are "learnt" properly, you shouldn't have any issues. But while the learning process the car would hesitate when going leaner and richer at low speeds...

    On my vehicles, I have seen them be a GOOD 2 to 3 miles on each before going back. This could work as a lean cruise actually. But it will revert to 13.3 negating the leaner effects.
    "All that is needed for the triumph of evil is that good men do nothing..."

  10. #10
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    Some info from a GM tech guild article on euro 3 emissions.


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