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Thread: l29 misfires vortec black box

  1. #16
    Fuel Injected! ralmo94's Avatar
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    Only new parts not mentioned in first post is new clevite 77 rod bearings, new piston and rings for number 3,
    New cooling system and gaskets.
    How are you supposed to do a crank relearn? Never done one before,
    But seen the option in hp vcm scanner.

    Happens open loop, closed loop, as rich as 11 to 1, and lean as 16 to 1, and stoch.
    Seems to be noticable as soon as idle comes down when warming up from a cold start.

    It does have a 180 thermostat with an eighth in hole drilled in it. Temps run pretty consistent at
    178, until pulling trailer up a grade. Miss was still there before the new t stat though, just thought it was dizzy wear.
    I did not check for slop at the chain. Wish I would have while the plenum was off.
    Valves appeared good when the head was off. Not hammered up like the piston and combustion chamber.
    Also took the lifters apart and cleaned them up, they were gunked pretty bad, but cleaned up well, and all rollers looked to be in good shape.

    Might have a picture somewhere of the head while it was off.

    Only thing that went to the machine shop in this half ashed overhaul was
    The number 3 piston and rod. Pressed rod on and wieght matched new to old.
    I think he said he got it within a half of a gram.

    If I was to try and experiment with injection timing, what would you recommend
    Targeting for EOIT? Stock it looks about 300 deg, wich is about 30 deg sooner than a stock ls.

    Everything I found about it seems to be for an over scavenging camshaft that
    Throws raw fuel out the exhaust. Would I want to target a little later closer to overlap,
    Or bake one the closed valve longer?

    I have put about 15k miles on the truck since, it now has about 155k on the clock
    Thanks
    Last edited by ralmo94; 02-03-2022 at 05:15 AM. Reason: added more

  2. #17
    Fuel Injected! ralmo94's Avatar
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    Found some pictures
    Attached Images Attached Images
    Last edited by ralmo94; 02-03-2022 at 05:13 AM.

  3. #18
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    Happens open loop, closed loop, as rich as 11 to 1, and lean as 16 to 1, and stoch.
    Seems to be noticable as soon as idle comes down when warming up from a cold start.
    How bad is the issue? We're talking a very mild stock engine here. Why would non-OEM settings for injection timing be necessary?

    Are you smelling excess fuel at the tailpipe? Especially cold? They always smell rich but is it burning your nose?

    Random misfire code set to no reporting because 454 is poopoo for smooth idle in OEM form and GM doesn't want to deal with complaints. They've always had a "half-assed misfire" in stock form ime. L19's were much worse but L29 still does it. The engine idles smooth for a bit then hiccups once or twice then is smooth for a bit. Over scavenging at idle? With a stock cam? Maybe? I'd be more inclined to believe it's post combustion gasses that failed to exhaust properly and are left to dilute the incoming mixture. Either way, if this is the issue and you feel you have to have it fixed I'd consider changing to an aftermarket cam. Or maybe increase idle speed slightly to just cover it?

    Was the head re-used without being cleaned up? If so there's a possibility that sharp edges are getting hot and affecting combustion timing. That may be hard to detect at idle without a way to measure crank speed or without a scope to view spark pattern. I'm reaching but without being at the truck it's hard to say which direction to go.

  4. #19
    Fuel Injected! ralmo94's Avatar
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    It's not terrible at all, just hard to sleep with engine running for heater, and a little annoying to hear out the pipes.
    I'd say hickup would definitely describe it.
    I don't believe I have over scavenging, I was saying that's what people normally adjust injection timing for.
    I cleaned the head up best I could with sand paper, it did not go to the machine shop.
    Do you think it's just a symptom of them having the cam retarded at the assembly line?
    I have raised the stock idle from 550 to 625, I might try a little higher.
    My main concern for starting this thread was that a couple injectors might have came out of there bores slightly,
    After everything that has been said here, I feel comfortable that I most likely don't have that issue.
    I do plan on getting an aftermarket cam, and new rings on the other 7, maybe this summer, or fall.
    Sounds like I just need to live with it until then.

    Thanks

  5. #20
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    454 can be tough to smooth out at idle. Do you have any tuning tools? Other than a cable they can be had for free these days. Can you get datalogs of the event happening?

  6. #21
    Fuel Injected! ralmo94's Avatar
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    Quote Originally Posted by 1project2many View Post
    454 can be tough to smooth out at idle. Do you have any tuning tools? Other than a cable they can be had for free these days. Can you get datalogs of the event happening?
    I have VCM suite from HP Tuners, and vacuum gauge, timing light, wide band, and digital multimeter.

    I have since raised the idle speed to about 760rpm. its a lot better, and smoother, but still there..
    I'm not sure if it showed up in the log or not, i'll have to review. I'll see if I can post up a csv of idling log.

  7. #22
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    Someone else will have to review an HPTuners log. Unfortunately I do not have that software.

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