Hesitation/Stumbling... PULLING OUT MY HAIR!

Discussion in 'GM Powertrain' started by moogvo, Aug 5, 2012.

  1. moogvo

    moogvo Epic Member 5+ Years 1000 Posts

    I have been chasing a hard starting hesitating/stumbling problem for MONTHS on this truck and can't seem to make a lot of headway...

    So, when the truck is cold, it runs like a raped ape. It has plenty of power/ once it gets up to operating temp, I noticed it to be hard to start and it has a lot of hard starting issues. I replaced the fuel pressure reg, fuel filter, plugs/wires/cap/rotor, PCV valve, EGR valve, EGR module, Ignition control module, coil, and all vacuum lines. After the fuel pump, the hard start has gone away. It is much more noticible when the A/C is on and in 3rd, 4th and 5th gears under acceleration. Throttle position sensor has tested good.

    It feels as if the coil has an intermittent loss of connection. It doesn't make any noises, backfires or rattles. This only happens when the truck is warm or when the air is on. I am ready to drag this truck out back and SHOOT IT!

    It idles GREAT. No problems there, although I DID clean out the IAC valve and the entire throttle body... Of course, the IAC valve would have nothing to do with any running other than at idle.

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