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Thread: Stumble on Acceleration with very lean readings from wideband

  1. #1
    Electronic Ignition!
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    Post Stumble on Acceleration with very lean readings from wideband

    Hey everyone to start off here is what has been done to my 1989 Chevy S-10 4.3 liter Vin Z Computer #1228062.
    *All cylinders bored 30 over
    *New Pistons (do not have in front of exact ones)
    *Comp Cams Cam,Springs,Hydraulic lifters and Roller Rocker arms Part # 09-420-8
    -Camshaft C43 270H-R10
    *96 and up Vortec Heads
    *2114 Edlebrock Performer Intake manifold
    *Stiffer spring in TBI Regulator that pushes pressure from 13 to 18.

    The Prom I have in the computer now is the stock prom with Main Spark table changes to more of a vortec type table and EGR dissabled. The problem that I am having is that when I fire her up she runs good at idle nice and smooth. I throw here in to drive and head out and for the most part runs fine no problems until I try to accelerate with the pedal more than half way down to WOT my truck stumbles and hesitates but then if I just give the pedal a little push it gets going accelerating normally. My wideband 02 sensor shows a really lean mixture during the stumble like somewhere around 22.3. I have attached my latest data log its not way long but shows the problem. Thank you for the advice and opinions in advance im pretty much at a loss at this point.reference.
    Last edited by S10Sanity; 01-26-2015 at 11:58 PM.

  2. #2
    Fuel Injected! brian617's Avatar
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    Try adding more TPS AE in at 20% at a time.
    89 K1500 Scottsdale 5.7L 5spd 3:42 RamJet cam Dart iron TBI heads 427 PCM swap
    95 C2500 Cheyenne 6.5L turbo diesel 4L80e 4:10 DB2-4911 Manual pump conversion 0411 PCM trans control 2Bar COS
    05 Outback XT 2.5L turbo gas auto

  3. #3
    Fuel Injected!
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    Quote Originally Posted by brian617 View Post
    Try adding more TPS AE in at 20% at a time.
    ^^ Except know you have Vortec heads and a large carb style plenum I would do both TPS and MAP AE values. I would multiply all but the lowest values in both tables by 1.5. I leave the lowest values alone because it seems to do weird things to the idle/off-idle tip-in if you

  4. #4
    Electronic Ignition!
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    Thanks for the replies guys I have been out of town for the past week so now I get to play around with this stuff. Thanks again.

  5. #5
    Fuel Injected! CDeeZ's Avatar
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    Found this thread and wonder if it pertains to the lean stumble I have on acceleration with the single plane intake TBI I'm working on dialing in.

    My stumble seems to mainly happen on 3rd gear shift of 4L80 when on it about 40%TPS, though it will stumble in other acceleration conditions when the throttle is opened up quite a bit/and or quickly opened......

    Tried hitting the tables mentioned above by multiplying by 1.3 and then again by 1.5...... Still stumbling.

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