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TBI guru needed... My TBI engine dies at stops in gear.. ???

Discussion in 'The Garage' started by uglychevyZZ4, Apr 17, 2003.

  1. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    Ok, I am officially stumped. this happened before the new engine, and still does it...

    My TBI 350 dies at stops in gear, the idle seems to be really low when in gear stopped at lights etc.. and it dies. I have tried to play with the timing but it is ecm controlled, so it just adjusts it back /forums/images/graemlins/rolleyes.gif /forums/images/graemlins/rolleyes.gif /forums/images/graemlins/rolleyes.gif /forums/images/graemlins/rolleyes.gif

    soooooo, I have even tried a new IAC ( idle air control ) and no difference
    /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif
    who has dealt with this? has new :
    plugs
    wires
    IAC
    egr gaskets ( egr was tested, its good)
    vacume lines
    cap / rotor
    no vacume leaks
    all new gaskets, no difference.. /forums/images/graemlins/1zhelp.gif
     
  2. Klink K5

    Klink K5 1/2 ton status

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    Your "check engine light on" ?
     
  3. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    nope, i FREAKIN WISH then Id have a lead / code and would be better off. runs purrrrrrty, til it dies. /forums/images/graemlins/smirk.gif
     
  4. Don

    Don 1/2 ton status

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    Is'nt there some sort of idle speed adjustment on the backside of the throttle body? /forums/images/graemlins/confused.gif
     
  5. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    no:( ecm controlled.
     
  6. 87sm465np208

    87sm465np208 1/2 ton status

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    try a new TPS, might solve your problem, made my friends truck idle at 2500rpm at stops in traffic, no joke, thought it was a vaccuum leak, turned out to be the TPS, id personally take it to autozone and scan it so you can see if anything is on the "off" side like not tripping a code, but not operateing at optimum level, or try your fuel filter, if she a'nt gettin no fuel to them injectors correctly she is gunna croke on you in traffic. /forums/images/graemlins/deal.gif

    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/truck.gif
     
  7. fortcollinsram

    fortcollinsram 1/2 ton status

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    I second the TPS... and maybe check you MAP...There is a screw adjustment that is under a plug on the TB that adjust the throttle stop, but DON'T, I repeat DON'T mess with it...you well screw more stuff up in the end by jacking with it...

    Chris
     
  8. fortcollinsram

    fortcollinsram 1/2 ton status

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    Does it die when you throw it in Neutral?
     
  9. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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  10. fortcollinsram

    fortcollinsram 1/2 ton status

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    hmmm....does it act funny at any other rpm and/or load levels?My guess is still with TPS or MAP

    Chris
     
  11. azblazor

    azblazor 1/2 ton status Premium Member

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    Are you running a VSS signal to your ECM?

    .....Without the VSS the vehicle may have stalling problems under certain conditions. The reason an engine not equipped with VSS may stall is because when the ECM has the signals that indicate the engine should be idling (foot off gas, vehicle moving less than 2 MPH), idle speed is closed loop ( which is not the same as the O2 sensor running closed loop) and the ECM will try to maintain a programmed idle speed. If the vehicle is moving, the ECM opens the IAC (idle air control) a programmed amount, regardless of engine speed, which is usually a position that will make the engine idle about 50-100 RPM above the programmed idle speed. Stalling can occur when the vehicle is in the over-run condition (foot off gas- engine speed above the programmed idle speed) because the ECM will try to lower the idle speed to the stationary programmed speed. The IAC may not be able to open rapidly enough to prevent the engine from stalling.
    Raising the minimum idle speed with the adjusting screw can eliminate stalling, but the engine will not run optimally without a VSS. (excerpt from "Chevrolet TPI & TBI Engine Swapping")
     
  12. jeffro

    jeffro 1/2 ton status

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    Throw a new idle air control motor on there. That sounds like the problem.
     
  13. bigbluek20

    bigbluek20 1/2 ton status

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    What tranny are you running? Could it be a sticky torque converter clutch (tcc)?

    Had that happen on a few cars. It is electrical, so you should be able to disconnect it to see if the problem goes away (torque converter just won't lock).
     
  14. outlaw612

    outlaw612 1/2 ton status

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    Sounds like the torque converter isnt unlocking
     
  15. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    [ QUOTE ]
    hmmm....does it act funny at any other rpm and/or load levels?My guess is still with TPS or MAP

    Chris

    [/ QUOTE ]no
     
  16. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    [ QUOTE ]
    Throw a new idle air control motor on there. That sounds like the problem.

    [/ QUOTE ]
    [ QUOTE ]
    soooooo, I have even tried a new IAC ( idle air control ) and no difference

    who has dealt with this? has new :
    plugs
    wires
    IAC
    egr gaskets ( egr was tested, its good)
    vacume lines
    cap / rotor
    no vacume leaks
    all new gaskets, no difference..


    [/ QUOTE ]
     
  17. Thunder

    Thunder 3/4 ton status

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    My best advise is to buy a scanner. You have already come close to paying for one with all the parts you bought.
    A scanner can tell you if your IAC is working, If the TC is locked, what the TPs and MAP are telling the computer and if they ar functioning.
    AN AutoXRay scanner only costs around 150 bucks. If you are going to work an a FId truck it will pay for them self the 1st time you use it.
    Scanners wont tell you everything that is wrong but they do tell you what isn't wrong so you dont replace parts needlessly. And help narrow down the trouble shooting area.
     
  18. florida4x4

    florida4x4 1/2 ton status

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    Check your VSS (vehicle speed sensor).
     
  19. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    [ QUOTE ]
    Raising the minimum idle speed with the adjusting screw can eliminate stalling, but the engine will not run optimally without a VSS. (excerpt from "Chevrolet TPI & TBI Engine Swapping")

    [/ QUOTE ]
    aside from the block, it is all original, down to the TBI ,ecm, etc...... the original engine did it and still does. So I shouldnt have to worry about adding something it should have,

    i think I got that, WTH is it? /forums/images/graemlins/rotfl.gif
     
  20. 90K5

    90K5 1/2 ton status

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    check the vacuum port on the intake manifold behind the tbi...mine was disconnected the other day and it did the same thing
     

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