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Thread: B3647 issue with COS5

  1. #1
    New Member
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    Mar 2021
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    8

    Default B3647 issue with COS5

    I am having an issue with the vehicle initially going lean in closed loop.
    This is an LSA supercharged 6.2 in my S10 with the factory 411 PCM.

    Upon initial start the air fuel is 11.5 which tapers to 13:1 as it starts to warm up according to my wideband.
    It appears the STFT initially pulls fuel & as soon as the transition to closed loop happens, the LTFT's ramp pulling a ton of fuel (to their set limit) until the wideband reads close to 19:1. After a short time the LTFT's are back to normal at a negative 1 or 2% where I want them.

    This only happens at cold start & usually is when pulling from a stop through an intersection where drivability is critical.
    If I get the vehicle moving before closed loop, it only shows up as a hesitation for a few seconds.

    I've tried altering the closed loop temp & time delay, but it still does the same thing, it just takes longer.

    I can reduce the LTFT limits, but I should not have to do this.
    If I make the values in table B3647 1's the problem goes away, but with a manual trans it likes some additional fuel during warm up.

    The values in this table are around 7.-.85 in most stock 411 computers.
    Can I no longer use this table in this manner?
    Is there something different I should be doing?

    Otherwise it starts, drives & runs great.

    Thanks for any help you can provide.
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    Last edited by Lonnies Performance; 3 Weeks Ago at 12:19 PM.

  2. #2
    Lifetime Member
    Join Date
    Mar 2006
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    Default

    What if you disable CL and only run OL?
    I have a weird issue with a truck drifting rich at idle over a few mintues. Give it throttle and it goes back to commanded Fuel from B3647. Give it a minute and Commanded afr drifts back rich and AFR follows.

  3. #3
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    Mar 2021
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    Default

    It is fine in open loop & also fine in closed loop, it just has an issue during the transition.

  4. #4
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    Mar 2021
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    I noticed in other 411 tunes, there is a B4206 which is an enable/disable for o2 correction in open loop.
    This is no longer available/shown in COS5, although I had it disabled previously in my base tune,

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