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2001 GMC Sierra rough idle in extreme cold...

Discussion in 'Truck & Equipment Repair' started by corey006, Dec 31, 2013.

  1. corey006

    corey006 Junior Member
    from al,can
    Messages: 8

    A couple of mornings ago my truck barely started, was plugged in and blockheater is working.

    In the past, When it gets close to minus 40 it used to sputter and hesitate just when I first started it but after it hit idle it was o.k.

    Well I went to work and plugged in and at end of shift it started but idle was all over the place surging, and then almost stalling lights going dim...I was able to get home and diagnosed a bad battery. I installed new one and truck started fine. I left idle for 20 minutes, then took for a drive and no problems.

    Plugged in and parked for the night and put a battery charger on.

    Next morning it was minus 40 again in started like it normally does but once idling was fine, no stalling.

    Went to work plugged in.

    End of shift same problem, sputtering and wanting to stall.

    got it home and put in garage(minus 10 in garage).

    Checked it 2 hours later and everything is fine.

    The night before I put some gasline antifreeze in and a can of seafoam, and filled the tank with premium gas.

    Only seems to be a problem when engine is really cold.

    Plugs at work are o.k but they are smart plugs on timers.

    The alternator puts out 14.8 volts at idle.

    So could I have electrical problem with voltage regulator,

    PCV valve freezing?

    fuel pressure problem

    throttle body, crankshaft pos. sensor, idle air control?

    Problem is intermittant so it will be tough to track down.

    I am going to start with fuel filter, and check fuel pump pressure I guess.

    But the lights going dim when stalling leads me to think electrical fault(maybe bad regulator on alternator) causing spike my voltage meter cannot read???


    2001 GMC sierra 1500 5.3 4x4. 100,000 miles.
     
  2. chevboy167

    chevboy167 Member
    Messages: 96

    Ah yes..... time to replace intake gaskets. As well as the 2 knock sensors and sensor wire harness under the plastic plenum. But try to snug the plenum bolts up first, that may help you to diagnose if that is the problem. It did on mine! Now these bolts have torque stops on them to prevent over tightening but you can still get a twist out of them. Just take caution and use one hand and common sense when trying this. Hope this helps and good luck... we're pulling for ya!
     
  3. silvergoat

    silvergoat Junior Member
    Messages: 1

    check for low voltage causing the Fuel pump not to pump full pressure? Or bad fuel pump.
     
  4. chevboy167

    chevboy167 Member
    Messages: 96

    Any updates on the problem/solution???
     
  5. zlssefi

    zlssefi Senior Member
    Messages: 117

    I have the exact same problem on a 2001 sierra 3500 with a 6.0. I also thought it was intake gaskets, but the local mechanic did the smoke test and found nothing wrong. They did find the air intake temp sensor in the MAF sensor wasnt reading and replaced it. We have two more storms coming so I have to try it out then bring it back if its not any better. Once mine was warmed up it always ran fine, just when it was cold the problem occured.
     
  6. onehot23t

    onehot23t Junior Member
    from Philly
    Messages: 1

    It sounds like the intake gaskets. They only leak when stone cold. Once you get just a little heat into the heads the leak stops. I see this all the time. If you scan it there is usualy a lean code P017? but no check engine light. A fresh set of gaskets and clean the throttle while it's apart will do wonders.