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Discussion in 'The Garage' started by deadtoyou, Dec 27, 2005.

  1. deadtoyou

    deadtoyou Registered Member

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    I drive a 1991 olds bravada with the 4.3, its got 256000 miles on it but ran really good and still does except at idle. it now shutters really bad like it wants to die but doesnt. it does this up until i get to about 30 mph and it runs perfect, any ideas of what the problem is? thanks in advance!

    - Dave
     
  2. dremu

    dremu Officious Thread Derailer Premium Member

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    Might have better luck looking for places that cater to the S-10/15 trucks, like http://www.s-series.org. This place tends to focus on the full-size (V8 trucks), and yours is a variant of the little ones.

    That said, I'm inclined to suspect the EGR valve, if so equipped. I seem to recall that you can take them apart and clean carbon out... just heard that, as my herd are all too old or too smoky (diesel) to have such things.

    -- A
     
  3. uglychevyZZ4

    uglychevyZZ4 3/4 ton status

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    could be one of many many things, too many to diagnose over the net, sounds like possible tranny issue if its a shudder only when driving or in gear???
    • does it do this in neutral / park?
    • do you have any check engine lights on?
    • have you gone to Schmucks and used thier FREE scanner? (its free)
    • whats the trans fluid look like? has that ever been serviced? ((no i dont suggest doing this at 256k if its never been done, bad idea))
    • any other odd actings?
    • have you checked for any vacume leaks?
    • reach under the EGR pot and depress it with your fingers and see what happens, does the idle change? smooth out?
    • has it been tuned up? recently ((last 30k?))
    • describe the shudder, is it a choppy missfire or is the whole truck shaking? or is it a shudder like a brake pulsation?
    • has the IAC ((idle air control)) ever been changed, or even cleaned out?
    • how old is the o2 sensor?
    • fuel pressure? is the pump noisy at idle? ((youd hear it in the cargo area more than normal))
    Sorry for the long list but I just tossed out immediate things Id look for if it was mine, but then again Knowing the shudder feeling, you have an advantage.. plus, these are all things everyones gonna ask you if you keep this thread going. So... might as well print off your check list to work on :D
     
  4. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    i've got a 95 blazer w/ the 4.3, and i have had trouble with the egr on a regular basis. it does have trouble idling when the truck gets carbon stuck in the egr. does it throw an emissions code at you thru the obd II sensor? for me, i've had very good luck reving the motor up to about 4 grand and holding it there, this tends to pass the carbon and the check engine lite will shut off not too long afterward. This can also be done by going WOT from a stop lite, and that typically removes the carbon. I've only had to actually pull the egr once, but it's not a very difficult thing to do. Incase you're not familiar, it's located just below the intake port of the intake manifold on the front of the motor. good luck.

    colby
     
  5. HarryH3

    HarryH3 1 ton status Author

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    Mine's a 91 S-Jimmy, basically the same rig with a different transfer case. I had a similar problem a few years ago and only found the cause by accident. The tiny spring that holds tension on the heated air flapper in the air cleaner had broken, letting it flop around. When closed, it would freak out the MAP sensor and cause the engine to run really rough.

    BTW, does yours have the factory compass in the rearview mirror? I nabbed one out of a '92 Bravada at the junkyard, but haven't been able to find the calibration instructions. If your owners manual has that procedure, I'd sure love to get a copy! :)
     
  6. deadtoyou

    deadtoyou Registered Member

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    Sorry, i should have posted at an s10 site but I come here with problems with my k5 and you guys help alot so i thought id throw this one out there. anyways thanks for all the input, i think itll help alot. Harry i wish i could help you but i dont have the owners manual, sorry and thanks again!!
     

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