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TBI Motor Problems

Discussion in 'The Garage' started by bassin4507, Oct 29, 2004.

  1. bassin4507

    bassin4507 Registered Member

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    MY 91' K2500 has been acting strange lately. It has no codes showing up, but sometimes when it idles it will idle from 500-1000 RPM for no reason, and it has a stumble when under load, it will clear out if you give it over 3/4 throttle. I checked my cap, rotor, plugs, wires, changed fuel filters and an air filter. I installed a fuel pressure gauge and the fuel pressure stays constant when it stumbles.
     
  2. tx_sub

    tx_sub 1/2 ton status

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    check for vacuum leak. i'm chasing down a similar problem. i;ll let you know if i find anything. i hopw you'll do the same. /forums/images/graemlins/burb.gif
     
  3. bassin4507

    bassin4507 Registered Member

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    What is the best way to check for vacuum leaks besides, just looking at the hoses for cracks, holes, cuts, etc. ?
     
  4. tx_sub

    tx_sub 1/2 ton status

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    yea, check your hoses and vacuum lines. another thing i'm doing tomorrow is spraying carb cleaner around the base of the tbi. its supposed to either change idle characteristics or bubble. i'm not sure, but i figure i'll know when it happens. other things to check are the egr diaphram and cruise control diaphram sticking. check throttle linkage, tps sensor. see if your computer is throwing a code too.
     
  5. Thunder

    Thunder 3/4 ton status

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    Distributor Module?
     
  6. Jays Beast

    Jays Beast 1/2 ton status

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    I am having a simular problem with mine. When yours is under load and stumble what sounds does it make? Mine sound almost like a backfire. I also have no codes, so I am thinking about changing out the distributor and checking the timing chain. Not sure where else to look for the cause of this problem.
     
  7. y5mgisi

    y5mgisi 1 ton status

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    Mine mdid kinda the same thing. Mostly it did it in th mornings backing out of the driveway. It would load up and act like it wanted to kill it self. Wound up being the EGR valve. It would be easy to test just unplug the vac line that goes to the egr and plug the line and see if it still does it. /forums/images/graemlins/deal.gif
     
  8. bassin4507

    bassin4507 Registered Member

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    I don't notice any different sounds when it stumbles, the motor is only 1 year and a few months old, all the sensors are the same age except the EGR is about 2 months old. I'll have to check my distributor.
     
  9. 91GMCSuburban

    91GMCSuburban 1/2 ton status

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    I would check your IAC. It may not be producing a code, but may still be mechanically bad.
     
  10. bassin4507

    bassin4507 Registered Member

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    I checked for vacuum leaks, and there were none. Next I pulled my plugs again and noticed that the gap on all of them was bigger than .035 so I re-gapped my plugs down to .035, and ran some Sea-foam through the motor, and the problem has completey gone away.
     
  11. Jays Beast

    Jays Beast 1/2 ton status

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    Glad to here ya got it running good.

    [ QUOTE ]
    I re-gapped my plugs down to .035, and ran some Sea-foam through the motor, and the problem has completey gone away.

    [/ QUOTE ]

    What is sea-foam? I /forums/images/graemlins/dunno.gif
     
  12. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    Jay , Marine supplys and some auto supplies have this stuff Clicky
     
  13. bassin4507

    bassin4507 Registered Member

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    It works real good as far as I can tell. You can either buy it in and spray can, or a regular can. The directions say you can put it in just about anything from small motors to big. I just sprayed some into my throttle body while it was running. On my 78 K20 I disconnected the brake booster vacuum line and poured some in there while the motor was running. Then I shut it off for about 5 minutes and it smoked quite alot (it's supposed to) and ran better afterward.
     

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