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Thread: Big off idle stumble, whatt first? IFR? calc.vet? Something else I'm missing?

  1. #171
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    I did measure EGTs when I got home from work before I shut the motor down. I had to do it twice because they dropped a bit over the course of checking them, but stabilized at the values below.

    380s 380s
    480s 480s
    480s 480s
    380s 480s

    I redid the cold ones and a few warm ones a couple of times to make sure there wasn't a variable like engine fan affecting things, but those values were very consistent. I swapped O2s last night and will take a log tonight and will be watching decel. I'm expecting that to remain the same. Next will be swapping injectors bank to bank and noting where they were and where they're going to see if the injectors are to blame.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  2. #172
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    Well the problem definitely stayed on the left bank, I went for a quick log that ended up around 8000 frames, this time with WBO2 reading. Check frame 3700 for my first of the 2 big decels I performed, seems to be a 5+ second delay before things go haywire just like in the last log.

    Statesman Log MAF Only O2 Swap.efi

    So I think the next logical step is to swap injectors bank to bank like you said, but track where they go and put the injectors from the cold cylinders into corresponding warm cylinders on the opposite bank to make sure there isn't something that follows there too. It seems to do it on all decel events and not just the big ones, more like a matter of throttle off time that seems to be driving it as it happens at 1500 RPM lifts too. I think I'll unplug the PCM connectors, shoot all the injectors, and jiggle the harness around to make sure there isn't something wrong in there as well.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  3. #173
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    that VE Table looks very very weird.... kind of like if the columns are rows and rows columns....
    you have your dynamics B0120 set to 4000 so the ECM is using both... wrong maf (too much fuel) coming off from a stop and you will have the stumble... is there a log of the stumble?

    (im on the first page) looking at the tune posted in the first page still.... Your PE enable B3616 is set to 70%. at a lot lower pedal you will get into boost, might be part of the cause for the stumble
    Injector data in general just looks wrong....

    If this has all been addressed, i apologize.
    "All that is needed for the triumph of evil is that good men do nothing..."

  4. #174
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    Stumble is gone now, just trying to clean up the rest of the tune. Truck actually runs the best it has since the blower went on. Stuff is obviously still wrong though, my injector data must have been off and then that screwed me on my calc.vet. Among other things. I should also point out, especially to Statesman, that my wideband sensor is on the driver's bank.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  5. #175
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    I need to upload my logs when I get home. I tried taking a different route, but far as I can see my results were inconclusive. While driving, I disabled 1, 3, 5, and 7 one at a time to see if the jagged logs went away. They did for a few seconds, then they came back. I tried it on 2, 4, 6, 8 and got the same result.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  6. #176
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    You need to do the bank to bank injector swap. Until you do that, you won't even know for sure if it's definitely an injector issue you're chasing.

  7. #177
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    I did already, my most recent logs are post sensor swap. Kid's on the laptop now.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  8. #178
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    Quote Originally Posted by Supercharged111 View Post
    So I think the next logical step is to swap injectors bank to bank like you said, but track where they go and put the injectors from the cold cylinders into corresponding warm cylinders on the opposite bank to make sure there isn't something that follows there too.
    Did you do that?

  9. #179
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    Nope, took the logs and left it at that for the time being. I wanted to make sure there wasn't something there I'm not seeing before moving the injectors around. Of course I managed to forget to post those yesterday once the laptop opened back up. I've been a bit distracted the last few days getting a new rear main seal into the dually and all the "since I'm in there" stuff that goes with that. Headed straight to the dually today after work, I made myself a reminder to post the logs tonight when I do get home.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

  10. #180
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    OK, here are a couple of logs I grabbed. This one is while driving and I shut off 1, 3, 5, 7 one at a time. On this one 1, 3, 5 appear to react similarly and disabling #7 is where it gets jagged. This was the cold hole when I lasered the header. Turns out my memory failed me and the front 2 were much less significantly cooler than I initially reported. I disabled 1 around frame 1188, 3 around 1479, 5 around 2125, and 7 around 2663. It looks like the WB is tracking with the NB on the left bank, but the logs are a bit deceiving with the way the NB spikes are so much larger than the WB.

    12 16 21 26.efi

    Next is one I took idling in the O'Reilly's parking lot and it's the right bank.

    120 500 900 1200.efi

    I took this for 2 reasons: 1 I saw the right bank go nuts when I disabled a cylinder on the left bank and 2, I noticed it going weird on its own. The truck needs to be driven a good 20 minutes before this starts showing up. On the left bank, because TP and load are constant, I can see that I disable cylinder 2 from frames 126-343, cyl 4 from 505-753, cyl 6 from 885-1020, and cyl 8 from 1253-1463. I'm curious to see if anything jumps out at you from these or if I'm misinterpreting something that's right in front of me.
    1998 GMC Sierra K1500 5.7/4L80E, longtubes, 411 w/COS 5, marine cam/intake, Whipple. 91 octane at 6000'.
    1997 GMC Sierra K3500 7.4/4L80E, 411 w/COS 3, Whipple, small cam.
    2004 Corvette Z06 with longtubes.

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