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2001 C3500HD Issue

Discussion in 'Chevy Trucks' started by White Gardens, Oct 2, 2011.

  1. White Gardens

    White Gardens 2000 Club Member
    Messages: 2,665

    Trying to figure out a gremlin that is causing me fits.

    My C3500HD, with an 8.1 gasser has been doing a funny thing this past year.

    If I start the truck and let it idle for more than 5 minutes, it doesn't want to really go when I put it in drive.

    It acts like it's starved for fuel, or just not firing right.

    As soon as I pull over and shut the truck off for 30 seconds, I can start it back up and it drives fine.

    I'm getting no check-engine light, power loss light. We ran a full diagnoses and tests just last spring and it only showed that one cylinder had a miss-fire at idle. Since then I've done a tune-up with wires and plugs, but haven't run a diagnostic since then.

    Any thoughts before I run another diagnoses?

    Thanks.

    Nick
     
  2. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Have you checked the fuel pressure?
     
  3. White Gardens

    White Gardens 2000 Club Member
    Messages: 2,665

    Fuel Pressure Regulator, Fuel Filter, Fuel Pump, Transfer pump, and rear sending unit have been replaced in the past year, but I haven't hooked a gauge to the fuel rail to see what readings I get.

    It was happening before the fuel pump replacement also.

    ...
     
  4. 496 BB

    496 BB Senior Member
    Messages: 789

    Have you ever changed the Crank Positioning Sensor? If not I would start there since that was a major thing for early model 8.1L's. Also in your sig it says 8.1L (492)....its actually a 496ci ;)
     
  5. White Gardens

    White Gardens 2000 Club Member
    Messages: 2,665

    Ooops, don't know why I put 492, thanks for the heads up.

    Yes, have replaced the crank sensor also. Just funny how this thing acts up only after it's idled at cold start up.


    ...
     
  6. 496 BB

    496 BB Senior Member
    Messages: 789

    What kind of plugs you use?
     
  7. White Gardens

    White Gardens 2000 Club Member
    Messages: 2,665

    AC Delco. Went with the cheaper wires though to save about a 100 bucks. The truck runs better and is smoother at idle since the tune up, but the power loss after idle at cold start up still comes back occasionally. The Plugs I pulled had heavy white deposits on them. They also didn't show signs of fuel or valve problems.

    ..
     
  8. 496 BB

    496 BB Senior Member
    Messages: 789

    Did you gap them at .050"? Stock gap is 60 and I run 45 but I also have alot of tuning. 50 is the best to run these at for stock. I dont think thats the problem though...just some FYI.

    So after idle does it run rough or put or it just feels down on power? Alot down on power or just a little? I feel this sometimes on mine too but mine is related to other things. Im wondering if it is something in the fuel tables in the programming or if it is going into Knock ****** all the time from something like a bad sensor or something. I would suggest talking to B&B and seeing his thoughts. He has an 8.1L too and hes my computer go-to nerd for all that high tech sh!t....lol. Hes good.
     
  9. White Gardens

    White Gardens 2000 Club Member
    Messages: 2,665

    I went ahead and with with a 60 gap as recommended.

    Basically it seems like it goes into a limp mode, or like you said, just ******** on the timing. I can basically get it to barely go at all. If I try it and it does it, I just pull over, turn the truck off, wait a few seconds and start it and it's back to normal.

    That's why I'm leaning towards a program problem. I'm also going to run a diagnostic test again and see if I still have the one cylinder misfiring at idle. That is what I'm wondering is the issue. It makes me think that if the engine is sensing a misfire it starts to mess with the fuel mixture or timing.

    ...
     
  10. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Nobody here recommended .060".
     
  11. 496 BB

    496 BB Senior Member
    Messages: 789

    Do a check on the trans computer also. What are you using to run checks? Tech II or EFI Live or what? Has anyone ever programmed the truck with a tuner?
     
  12. White Gardens

    White Gardens 2000 Club Member
    Messages: 2,665

    No programing has been done. The checks have been done by my Mechanic who has a full GM scanner that he can check the live diagnostic.

    ...
     
  13. 496 BB

    496 BB Senior Member
    Messages: 789

    Pay attention to knock sensors and knock ****** if he does a test while driving. Tell him to flash the computer with the latest updates as there were a few for the TCM not sure about the PCM. Nothing major though.