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Carb or Dist.

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Chevit, Jan 26, 2004.

  1. Chevit

    Chevit 1/2 ton status

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    I have been having problems with the old Blazer and do not know if it is the Carb. or the Dist.
    It will run fine then all of the sudden it with stumble on aceleration, and if I give it more throttle it will pop up thru the carb. If I feel it start to stumble and keep it at the same throttle it will stumble for a few and then recover with a slight surge and run fine untill the next time. The only thing I have done to try and correct this problem is replace the fuel filter and spray some carb cleaner in it. At first I thought it could be my vacume advance but it does this same thing at idel. Any ideas???
     
  2. Confedneck

    Confedneck 3/4 ton status

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    what kind of carb, what kind of ignition? HEI? coil setup??
     
  3. Chevit

    Chevit 1/2 ton status

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    quadrajet, HEI
     
  4. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    When's the last time you did a tune up? It sounds like your problem is more spark-related than fuel-related.....

    If it's been more than a couple of years I would replace the cap/rotor, plug wires and spark plugs. I had a similar issue a few years ago and I traced it to a couple of faulty wires.
     
  5. Chevit

    Chevit 1/2 ton status

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    I did a tune up about seven months ago. The only thing that has not been replaced is the dist. Swaped the motor about 80,000 miles ago, got a rebuilt carb about two years ago. Changed the cap, wires and rotor not that long ago.
     
  6. Confedneck

    Confedneck 3/4 ton status

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    do you have the vacuum advance hooked up to full time vac or part time??
     
  7. Chevit

    Chevit 1/2 ton status

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    I guess full time vac advance
     
  8. Confedneck

    Confedneck 3/4 ton status

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    your vacuum advance requires that you have minimal vacuum at idle, not full.. that could be causing a problem..
     
  9. Chevit

    Chevit 1/2 ton status

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    I take that last post back, it is hookrd up whatever the way it come stock...
     
  10. Sandman

    Sandman 3/4 ton status Author

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    The timing might have slipped on you. I had this problem an the timing had slipped quite a bit (loose distributer). Maybe you could check that.
     
  11. Chevit

    Chevit 1/2 ton status

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    After checking the intake bolts, bolts on the carb. vacume lines ect... /forums/images/graemlins/thinking.gif drivers side rear plug wire was almost burnt in half... /forums/images/graemlins/doah.gif
     
  12. Chevit

    Chevit 1/2 ton status

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    Well it ran fine all day yesterday and this morning it started to act up again. Is there anyway to check out if the dist. is working OK? It is the original dist. with 200,000 + miles on it...
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    Do you ever notice that your idle RPM is kind of random, varying within a few hundred RPM's each time you stop?

    I'd probably pop the cap off the distributor and check that the mechanical advance weights aren't bound up. A high mileage dist. of mine had messed up mechanical advance weights, and they were binding at times...idle was ok, but varied, and I had some backfiring on acceleration at times as well.
     
  14. Chevit

    Chevit 1/2 ton status

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    I will check it out I have thought this was the problem all along. I did put some lithium (sp) on the wieghts awhile back thinking this might cure this problem.
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    They have pressed in plastic "bushings" they are supposed to ride on, but they can (and do sometimes) break up, which either makes a rough surface for them to slide on, or with the additional height of the bushing gone in places, the bushing can bind on the post it pivots on.

    Mine were obviously screwed up, the holes in the weights that they pivot on were really worn out, and one weight would end up on top of the other one. /forums/images/graemlins/smile.gif

    It's easy enough to check, but don't lose the springs on the weights. You can buy advance curve kits, but no need to unless you feel like messing with it. AFAIK there is nowhere to get those little bushings though. Maybe someone else has a source?
     
  16. Chevit

    Chevit 1/2 ton status

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    or could it be my EGR valve???
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    Tyically EGR problems are noticed at idle and cruise, not acceleration. Of course anything can happen, it's a valve that can get stuck in any position it wants.

    However, backfiring through the intake means the mix is igniting before it gets to the cylinder, EGR has no effect on that. EGR serves only to dilute the engines incoming air.
     
  18. Chevit

    Chevit 1/2 ton status

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    I put a timing light on it today and I had it way to advanced. So I set it at 8 degrees. There was no popping thru the carb. but sitting in drive way it would idle fine and then stumble, then recover. I also pulled the vac hose off the EGR and sucked on it and did not fell any vacume...
     
  19. dyeager535

    dyeager535 1 ton status Premium Member

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    I don't know how TBI stuff is set up. I would htink you have an EGR solenoid, which only allows EGR when the ECm sees the proper conditions. No vacuum to the EGR line at idle is good. If you press up on the bottom of the EGR valve, it should try to kill the engine. Not a concrete test, as it can still stick, but with the engine off, you can again try pushing on the underside of the valve, and "feel" if operation is smooth.

    Many problems can cause a stumbling idle issue, O2 sensor, IAC, bad ignition components (plugs, wires, etc) and so on.
     
  20. Chevit

    Chevit 1/2 ton status

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    Well I replaced the EGR it was bad but I am still having the same problem. I have the dist. cap off and when I apply vacume to the vacume advance the bottom weights move but not the ones on top should they??? /forums/images/graemlins/confused.gif

    One other thing when I start this thing up in the morning the engine will idle up and down quite a bit. I do not have the AC what ya ma call it hooked up so I know it is not that. After it warms up and is at idle it will do the same thing just not as noticeable or as quite often. /forums/images/graemlins/confused.gif

    Update: Just noticed the Ignition coil groundstrap was missing and the coil itself has a few arch marks on the metal what ever you call it where it goes into the back of the coil itself
     

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