1998" Chevy with Problem with a 5.7 Liter

Discussion in 'General Chevy & GM Tech Questions' started by brockrg, Sep 5, 2012.

  1. brockrg

    brockrg New Member

    What will cause my truck to fall flat on it's face while going up a long incline. It seems to run fine under normal conditions but when hauling a load or lately without a load it will start to shutter and won't take any fuel. I can put it in neutral and it will rev or I can just let off the gas for about 10 secs and then I can take off again. I have replaced the fuel pump within the year and it idles at 52 lbs and will climb to 60 under load. I replaced the head gaskets last year and the spider injection unit 3 months ago. I also replaced the cats last month. Nothing has touched the issue. I have no check engine light and nothing is showing up on the scanner. I'm lost!

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

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  3. MTM

    MTM Rockstar ROTM Winner 100 Posts

    I would say check your mass air flow sensor and maybe even your o2 sensors
  4. brockrg

    brockrg New Member

    Wouldn't the mass air flow sensor or the o2 sensor throw a code. Mass air flow was a concern of mine thinking that I may be starving or choking the air flow.
  5. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    Could this symptom also describe a transmission shifting problem? Maybe not shifting back out of overdrive and TC lock up problems?
  6. brockrg

    brockrg New Member

    Ok, I have replaced the spider, cats, trans filter, cleaned the mass air flow and entire air intake system. The fuel pressure idles at 52 psi and will reach 60 on demand, so what is causing this thing to still break into a shutter when placed under a load typically heading up on long grades. I can take out of over drive and place it in third and I have the same results. If I place it in neutral I can rev it but if I put it back in drive it will still shutter. This is what really doesn't make sense, if I let off the pedal for about 10 to 15 seconds I can take off again like nothing ever happened. If it was the trans would it recover in 10 to 15 seconds? I don't think so?? I put it on the scanner today and there are absolutely no codes showing, not even in history. I can make this happen almost at will. My last thought is the torque converter but I would think there should be a check engine light?? Help
  7. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    The under load for prolonged period is what made me think transmission and that included the torque converter but now I am out of suggestions. It would be good to know if the problem was engine or trans. related. If it were me, I would find a way to monitor fuel pressure under those conditions. Find a way to get a gauge to be veiwed by passing the hose between hood and windshield so you could see it while driving. Keep it outside the cab,, fuel under pressure inside is a dissaster waiting to happen. Is there a way to disconnect the TC lock up electricaly just to see if it is related to problem?
  8. brockrg

    brockrg New Member

    Thanks DPeter, I have already connected a fuel gauge to the windshield wipers and ran it under load and during the failure mode also. The pressure increased to 58-60 lbs during the load period and never flickered during the failure, which in my mind ruled out the fuel pump? I'm stuck on the torque converter but I'm not sure that it could recover in 10 to 15 seconds?
  9. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    If it's the TQ, you should be able to dup the condition on the level by applying a load, like adding a bit of brake while driving.

    I don't think it's a load problem, shifting to 3rd should fix it.

    If only happening while going up hill, it must be caused by something shifting due to gravity. But what?

    No codes, so it can't be an engine management problem, but it could be an engine supply problem (air, or fuel).

    I think you've tested for fuel, could anything be cutting off the air?

    Could something mechanical be moving enough to load down the engine, like maybe in the diff......check the fasteners at the rear axle.

    Could gravity be causing a fuel pickup problem?

    Just some thoughts.
  10. dpeter

    dpeter Epic Member 5+ Years 500 Posts

    Well OK then, not a fuel issue for sure. Hopefully someone with a more intimate knowledge of the workings of this truck will stumble across this and have an answer for you. The only thing I could suggest is to get a scanner that you could hook up and read real time data while this is happening in hopes the problem would reveal itself. http://www.scantool.net/ this site has some capable units and pricing from good to OMG.

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