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1999 GMC 3500 7.4 Vortec stumbles on take-off

This is a discussion on 1999 GMC 3500 7.4 Vortec stumbles on take-off within the Technical / Maintenance forums, part of the General Discussion category; Hello I Have a 1999 GMC 3500 7.4 L Vortec owned it since new it has 212,000 Mi on it ...

  1. #1
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    1999 GMC 3500 7.4 Vortec stumbles on take-off


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    Hello
    I Have a 1999 GMC 3500 7.4 L Vortec owned it since new it has 212,000 Mi on it
    and I've been chasing a problem for a year.
    Hoping someone can shed some light on my issue?
    I have a Stumble Hesitation at take-off only this is magnified when pulling my 5th wheel 10- fold.
    When by it self it's intermittent.
    I've changed distributor OEM cap wires throttle position sensor Mass air-flow all OEM
    Fuel pump assembly.No change in performance?
    Now I have put a fuel pressure gauge on the truck when running got reading and shut it off and the pressure dropped off. I was told this was a leaking regulator since it's not easy to get to and not sure this was the real problem I've avoided going there for cost reasons.
    please help if you've ran into this .

    Thank you Daryl

  2. #2
    Registered User Totty's Avatar
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    Re: 1999 GMC 3500 7.4 Vortec stumbles on take-off

    it's not that bad to change. I just did mine last weekend. you will just need some snap ring plyers to get to it. Also, those motors are bad for the injectors leaking. Most places won't even rebuild them. Catch yourself up on the "7.4 big block" post in the very top of the maintenance section. You will learn a ton.
    1999 GMC K2500 Suburban 454
    285/70/17 Duratrac's on H2 Wheels

  3. #3
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    Re: 1999 GMC 3500 7.4 Vortec stumbles on take-off

    The fuel pressure regulator is your issue GUARANTEED. Easiest way to deal with it is to remove the plenum. Should take about 3 hours to remove and remove the first time. Once you do it once or twice its easy. I can get mine off in about 30 minutes now. While your in there get rid of the factory injectors. Go with either the ford motorsport injectors as spoke of in the 454 forum or do what I did. Put a set of 98-00 LS-1 Injectors in it. (GM# 125558894) They work great and are a drop in replacement no tuning required. Oh with the plenum off put a coil on it. I hope you put AC delco Platinum plugs back in as they run the best in our trucks.
    CCLB dually, LS-1 Injectors, Airaid Intake, Magnaflow 2.5 dual in/out, Derale Cooling Tube Pan, B&W 24K super cooler[


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    Re: 1999 GMC 3500 7.4 Vortec stumbles on take-off

    Thank you
    I'll get on it just was hoping was something easier!

 

 

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