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

  1. #111
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    Transmissions really aren't my thing. Hopefully someone else will be able to jump in and help you with it.

  2. #112
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    I looked at your tune, looks like in your part throttle that Normal+Cruise are set the same and Performance+Hot are set the same. The low end is much higher than Normal+Cruise, try lowering these? Have you compared your settings to a stock tune with 4LO, I have a feeling that in 4LO the difference in transfer case ratio may be throwing your shift points off. 4HI is 1:1, 4LO has a multiplier (of what depends on transfer case).

    Log it and see what the shift status is when you're in 4LO, plus see when the PCM commands the shift.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, starting the mods
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

  3. #113
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    As far as I know, 4lo doesn't use any of those tables. There's a wire coming from the transfer case that tells the PCM it's in 4lo and then the PCM references that 4lo ratio to correct the shifts. I did copy a few of the normal tables to cruise for TCC and unlocking, forgot those were bugging me. So back in the day, the trick to to getting 4lo to work in the 411 was to start with a 4x4 S10 tune, then segment swap your engine and trans in, then make that into a COS. I believe this would require me to un-COS and re-COS and since I never use 4lo I've ignored it all these years. It still bugs me as an incomplete aspect of the 411 swap and I really thought the platform selection would be the simple version of what I just described as it was known to be buried in that segment somewhere. Maybe I'll try calling it a GMT800 and see what happens.
    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.

  4. #114
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    Ah got it, that makes (some) sense. GM making it hard, sigh. S10 base file as it has the transfer case ratio + 4LO setup. You'd have to start with that as a base, seg swap whatever's needed, then upgrade to a COS.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, starting the mods
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

  5. #115
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    Aaaaaand I think I just figured out why RAFPN/RAFIG wouldn't produce sane values for me when I did it before: I thought the output was a new value, not a corrective value that I add/subtract to desired airflow. After a reflash the truck does not want to idle until it gets up to temp and has time to learn. Though MAF/VE may be a smidge off since correcting IFR I think doing a quick RAFPN/RAFIG will get me a lot closer to correct now even after I redo those, which will happen after I deal with whatever is causing my O2s to go bonkers.

    Nevermind, I lied. Checked old RAFIG stuff and it wanted to cut around 1.5-2 g of airflow. For the sake of science I globally added 1 g/s to the entire desired airflow table and now over 2 different ECT ranges it's trimming 3.5 g/s. Not at all the right way to do it, but good to see if cuts more airflow when I demand more. Just doesn't make sense that it claims to be trimming air when, at times, it struggles to stay idling at all. Mostly after a start, but only occasionally. I suspect it's a mechanical issue and it's been beating my ass for a long time now.
    Last edited by Supercharged111; January 30th, 2019 at 02:09 PM.
    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. #116
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    Quote Originally Posted by Supercharged111 View Post
    which will happen after I deal with whatever is causing my O2s to go bonkers.
    Are you logging your O2 sensors?... do they appear to be switching rich/lean properly?

  7. #117
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    Quote Originally Posted by statesman View Post
    Are you logging your O2 sensors?... do they appear to be switching rich/lean properly?
    The right side, no. It was pretty well locked in at .457 for a good chunk of the time. The left side was reading lean and moved around more than the right side, but indicated a constant lean situation with only around 3.9% positive LTFT. The left sensor was new in September. Since the right one just took a shit, I've decided to figure out this damn misfire that's been absolutely plaguing me since I put the marine cam in. It was creeping on me before the cam, but after was 1000x worse and really impeded on driveability. Then as I drove it more, it got better. Last September the truck sat for about a month while I did a big round of maintenance on it and it ran like absolute garbage for the first 2 weeks after that. It really seems like I may have more than 1 mechanical fault on my hands which makes it very difficult to pinpoint. I had an extra cam sensor laying around so I threw that in tonight with a new rotor as that wasn't looking so hot and will drive a couple days to see if that had any impact whatsoever. I doubt it since I was just driving around with no cam sensor but I have to cross it off my list because all that remains that I can figure is that, a bad crank sensor, wiring, or a wallered out upper bushing in the distributor housing itself. Need to remove, disassemble, and inspect entire distributor to verify that. One thing I noticed that struck me as very odd was that it was idling around 16.5:1, so I disconnected the MAF. It then idled around 12.0:1. I kind of doubt the two disagree with each other that much, so I squirted the MAF with cleaner, put it back in, same thing. Going to dig up my spare MAF tomorrow and do another search for vacuum leaks. My last search for vacuum leaks was fruitless. Here's the log with cam sensor plugged in from a couple nights ago, you can see just how whack the LTFTs are. They were pretty happy way back when I did the calc.vet.

    Whipple Log 22 Cam Sensor Plugged in.efi

    The only code is for bank 2 not switching enough, is that enough to prevent the fuel trims from doing their thing?

    The more I think, the more I overthink. How are fuel trims applied? Globally or bank per bank? The engine measures the latter, so to me the latter makes more sense but it's not something I've ever thought about before.
    Last edited by Supercharged111; January 31st, 2019 at 04:49 PM.
    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. #118
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    I'll try to look over your log in the next day or two... but in the meantime, check your O2 heater circuit fuse and also check for any damage in the O2 sensor wiring. If the wiring is damaged, it usually happens in those hard to reach places... so check all the wiring thoroughly.

  9. #119
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    If NBO2 sensor wiring is soldered or spliced or heatshrink sleeved within 6 to 8 inches of the O2 sensor, the the O2 sensor may not be able to read free which it needs as reference.

  10. #120
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    Quote Originally Posted by joecar View Post
    If NBO2 sensor wiring is soldered or spliced or heatshrink sleeved within 6 to 8 inches of the O2 sensor, the the O2 sensor may not be able to read free which it needs as reference.
    Well. . . I did make my own O2 extension years ago. Weather just turned to crap. I think what I'll do first is inspect wiring. If I find nothing, or if I repair what I find to no avail I'll swap left and right O2s to see if the behaviour swaps sides too. I do have a manufactured O2 extension that I bought so I should try that too. Last September when I did the left O2 the right side was still happy.
    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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