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q-jet question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by scrapper, Apr 3, 2001.

  1. scrapper

    scrapper Registered Member

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    My 85 k-5 will not hold a smooth idle.I first thought that the throotle plate might be loose.But that seams ok.The question that I have is what is the electrical connetion on the top of the carb for,It appears as if this carb has some type of electric float.This must be some type of emmissions carb.My guess is that this is a fedback carb,but I have no 02 sensors ect..Can this be the problem with the idle?Can this be elliminated?Or is it time to replace the q-jet,with a older q-jet.Or just throw on a holey or edelbrock.The latter 2 would probably kill what is left of the 305.Then maybe it is time for the crate motor.
     
  2. WhiteWhomper

    WhiteWhomper 1/2 ton status

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    Unfortunately, the electronic Q-jets as you have are not much for adjustability, but they usually stay fairly in tune. I would first eliminate your ignition system as a cause of your idle problems before attacking the carb. Problems such as improper initial timing, stuck advance springs, improperly set dwell, bad spark plug wires, cap, rotor, etc. can all cause problems that look and feel as fuel related. Usually we all need a tune up anyways, so you might want to take some time with this area and see if that doesn't eliminate your issues. If you do decide that the carb has problems I believe that your best bet is to rebuild the Q-jet that is, unless your throtle shaft is worn out. Your Q-jet is really not that bad to rebuild if you take the time to do it right and the Q-jet is pretty reliable. This is a place that you want to buy a good rebuild kit. I have found that the kits from Napa are about the most complete and of good quality. If all that doesn't work, hit it with a hammer.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    There is nothing wrong with a Q-jet. See some of the posts on here, it is even suggested that the newer Q-jets are better than the older ones on angles. At any rate, I'm betting that plug (if there is only one plug) is the TPS, which is input for your transmission, cruise control, and likely a couple of other things. No reason to ditch it. Not good for your tranny to do so anyway. If you've only got one electric plug, your carbs primaries are still "mechanical" and do not have a computer to run them.

    Not smooth idle I would be looking for vacuum leaks first thing. Also, a symptom of a large vacuum leak (as in hose disconnected) is starting, but immediate stall of the engine when its cold.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  4. scrapper

    scrapper Registered Member

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    Before I ask these questions and fear the worst,I should look at the darn thing.The carb is a remanufactured unit that was intalled on he truck before I bought it.Well the bone head that installed it left the left rear bolt almost out,and the other three loose.It also seam to have the wrong base gasket.As far as the electric plug,I still think that it is somehow for the float bowel.
     
  5. HispanicPanic

    HispanicPanic 1/2 ton status

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    i have had all three carbs edelbrock, holley and q-jet so from experience stay with the q-jet becouse it has cener floating floats and is the best in my opinion for all the nasty angles we fourwheelers get our selves into if you do want an older carb get a q-jet from a 69 pickup 4 barrel q-jet at auto zone they work great man and only like 120.00 with a one year warr.

    NOT ALL HISPANICS DRIVE LOW RIDERS :-) <A target="_blank" HREF=http://jimjim.coloradok5.com>http://jimjim.coloradok5.com</A> mine is the orange one
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    There was NEVER an electric plug for the float bowl. The ONLY thing that the Q-jet EVER had that was electronically controlled was the primary metering rods. The TPS (one of two plugs the Q-jet could have had) has NO function except to tell a computer how far into the gas pedal you are.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     

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