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erratic idle

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Jonny-K5, May 9, 2006.

  1. Jonny-K5

    Jonny-K5 1/2 ton status

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    once and awhile i notice that my truck will "hunt" for a steady idle. it'll go from 500 something to 400 something.( i have a digital tach that rounds to the nearest hunderd). what could be the cause? IAC?
     
  2. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    Location:
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    Vacum leak, Messed up timing gear, bad fuel filter, plugged PCV valve, bad plugs, bad wires. bad coil. I could go on and on any more specifics like is it wet outside just when you stop only in hot weather etc etc etc.
     
  3. Desert Yeti

    Desert Yeti 1/2 ton status

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    My bet is a vacuum leak, but any of the above reasons are quite possible. :)
     
  4. FlatBackBlazer

    FlatBackBlazer Registered Member

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    Location:
    Spencer, Ma
    I just was having that same problem. My truck would stall coasting down the road but still ran decent when u had your foot in the gas . So i replaced my brake booster Filter and check valve . That did nothing, sooo i ended up rebuilding my Edelbrock carburetor and replaced the spark plugs. Found quite a bit of dirt and junk in the float bowls soo im guessing that may have been the culprit.After that i changed out the oil and cleaned my K&N air flilter. After a little adjusting of my carb all is well right?? Nope! I find out i had a tank full of Sand and about 2-3 gals of water. See i had a MTS plastic tank i got from JC Whitney and my sending unit is sitting on a rubber gasket ring and held down with 6 tabs and sheet metal screws. Pretty poor design, i think they should have just pressed in a steel threaded ring like the stock steel tanks have. Soo I ended up draining like 10 gals of gas/water/sand into buckets (using them to get the fri night bonfires going) Used Seal All Gas tank sealant on the gasket , then i used another gas tank epoxy putty stuff to fill in around the o-ring so water didnt sit in it . I ended up dropping like 140$ at Napa for all that stuff . Not tooo bad right ?? WRONG after rebuilding the carb once and pulling it off and cleaning it like 3 times w/ 3 new filters i thought i had the stumbling at idle cured. After about a week of smooth operation it started stumbling again and idling real low like 400 rpm to the point of shaking the whole truck. Turned the idle screw up some and its only idling really high . Sooo i try readjusting the carb , filter was clean and i get it idle decent again, but i hear an exhaust leak ticking sound on the passengers side . Header bolts are all tight, no visible cracks, manifold gaskets are in good shape . I cannot find where the leak is ! Im also losing coolant in the radiator , no leaks and its not in the overflow tank . i Read a couple threads and i think it may be a head gasket or even worse a cracked head! Im going to do a compression test and see where im at but i think i may end up purchasing a GM 350 HO crate motor for like $3500 . Pretty steep but im tired of dealing with all the problems my old 350 has been giving me. 330Hp is gonna be a nice upgrade though sooo i think im gonna do it . Any body wanna buy a used 350 in the New England area??? Haha
    i dont know if this will help anyone but i sure do learn alot by reading everyone elses trials and tribulations. CK5 is the only reason i keep my truck on the road and OFF !!
     
    Last edited: Jun 8, 2006
  5. Cricket

    Cricket 3/4 ton status

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    Location:
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    The manual says:

    1. vacuum leaks
    2. leaking egr or plugged pcv
    3. air filter clogged
    4. fuel pump not delivering sufficient fuel
    5. leaking head gasket
    6. worn timing chain
    7. worn camshaft lobes
    8. valve clearance out of adjustment
    9. ignition timing out of adjustment
    10. ignition system not operating properly
    11. thermostatic air cleaner not operating properly
    12. dirty or clogged injectors
     

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