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Sudden Idle change after wheeling, is it the Q-Jet?

Discussion in 'The Garage' started by morphed86k10, Jun 14, 2003.

  1. morphed86k10

    morphed86k10 1/2 ton status

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    After a bit of wheeling in the sand my engine is suddenly idleing at about 500 rpm, where it used to be ~750. I suspect a vacuum leak, but don't know where to look. Anyone have any advice on what to look for?
     
  2. georgiared84

    georgiared84 1/2 ton status

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    Did you suck any crap up into the air cleaner? On dry days, I've sucked enough dust and dirt into the air cleaner to do that.
     
  3. mosesburb

    mosesburb For Rent Premium Member GMOTM Winner

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    Typically a vac leak will increase idle (similar effect as truning idle screw in to let more air in). You may want to check out the distributor. Make sure the vac advance is working (dist cap off, create vacuum on hose port either with a vac pump or suck on a piece of vac hose connected to it, then hold tongue on hole and see if advance mechanism stays put or starts moving back to its original location). If it stays put, it's good. If it starts slowly retreating to its original location, it's bad. If that all checks out, grab the rotor and turn it to see if the mechanical advance is locked up. You should be able to turn the rotor a little bit (if you can't, it has a problem) if you can, release it from the point you turned it to and it should spring back to its relaxed position, if it does, it's cool--if it doesn't it needs to be cleaned out and re-greased. Remove distributor, disassemble, remove advance mechanism from the shaft (the part with the reluctor wheel on it), clean out old grease, install new grease, reassemble and see what happens. I find that many of my customers vehicles suffer from this condition. After servicing the advance mechanism, the vechicles usually run a whole bunch better. I'm not saying this is the problem, but it is sure easy enough to check out, and who knows, maybe you'll find some "free power".
    Good Luck
     
  4. CHEVY 4WD

    CHEVY 4WD 1/2 ton status

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    Ive had my q-jet do the opposite would idle up but after a wile of playing with it and the AC it would go back down BTW if you truck can idle at 500RPM why not lower your idle?
     

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