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Q-Jet Idle GREMLIN!!!! ******** Updated- FIXED!! *******

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Can Can, Apr 23, 2003.

  1. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    ******UPDATED*********

    Well, that ended up being an easy one to solve. I just got back in the house- it's amazing how much easier it is to see under the hood during the day/forums/images/graemlins/wink.gif!!!

    My problem ended up being a loose vacuum hose at the vacuum advance on the distributor. It was literally hanging on by a thread(I don't know how it worked itself THAT loose /forums/images/graemlins/tongue.gif). I pushed her on tight and the idle immmediately bumped up and smoothed right out.

    Thanks to all the guys who replied and pointed me in the right direction. You're good boys!!!! /forums/images/graemlins/grin.gif

    END UPDATE

    Up until about 2 weeks ago, my 84 was running fine. During cold starts she would jump into high idle and once she warmed up and kicked down it would idle nice and smooth. Idle was also smooth while driving around town and sitting at stop lights.

    HOWEVER, in the last 2 weeks the idle has deteriorated. High idle isn't all that high- it almost sounds like the choke is stuck on(but it's not). When I sit at a red light, the motor is barely turning. It really feels like a choke problem but the choke is working fine as far as I can tell.

    Here's the wierd part- I bumped up my idle speed a bit and it seemed to help, but only in Park, not Drive. Then I pulled into the car wash and my idle in Park was lower again........ /forums/images/graemlins/mad.gif /forums/images/graemlins/confused.gif

    I highly doubt this is a fuel supply problem because driving performance hasn't been affected. Acceleration and power are still the same.

    So what the hell is up????? /forums/images/graemlins/tongue.gif
     
  2. JIMs70K25

    JIMs70K25 1/2 ton status

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    Re: Q-Jet Idle GREMLIN!!!!

    Sounds like a vacuum leak. I had similar symptoms, problem ended up being a blocked off vacuum port on Q-jet had deteriorated and was leaking. Went ahead and replace all 3 vacuum caps.
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Re: Q-Jet Idle GREMLIN!!!!

    I checked all the vacuum lines out yesterday, but I'll take a closer look tonight. It does kinda feel like a vacuum issue.
     
  4. Goober

    Goober 1/2 ton status

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    Re: Q-Jet Idle GREMLIN!!!!

    It sounds like a classic Quadrajet vacuum leak to me, Paul.


    Check all your vacuum lines, spary a little carb cleaner around the base to check for leaks down there and double check your choke again. It's an electric choke on the '84, right? Check it first thing in the morning and adjust if necessary.


    /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
     
  5. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    Re: Q-Jet Idle GREMLIN!!!!

    mine was well is doing the same thing(I'm fixing it today) and i found out i had sucked a intake gasket so spray that carb cleaner or starter fluid around the intake gasket as well
     
  6. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Re: Q-Jet Idle GREMLIN!!!!

    I'll do a really good check of the vacuum lines, carb base and intake gasket tonight. I've already watched the choke operate and everything seems okay- it closes and when I start the truck it opens a hair. As the engine warms up the choke pulls off until it's fully open. I'm pretty sure that the choke is working properly......

    Here's another question, guys. When I cover the top of the carb with my hand when the truck is idling, the idle bumps up and smooths out. It seems to me that would indicate a lean running condition, but my performance is still great and it doesn't seem like I have a lack of gas. The only time I notice a problem is at idle.
     
  7. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Re: Q-Jet Idle GREMLIN!!!!

    Could be bad throttle shaft bushings...another famous Q-jet problem. Spray some carb cleaner or whatever at the throttle shaft area while it's idling. It might be cheating air in through there messing with idle.

    Generally if you cover the carb with your hand while it's idling it should die, or want to. If the idle smoothes out it's getting just enough air from somehwere else that it shouldn't be.

    Rene
     
  8. pilgrim

    pilgrim 1/2 ton status

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    Re: Q-Jet Idle GREMLIN!!!!

    i had the same problem. it turned out that i had the EGR valve hooked to manifold vac and not hooked up to the solinoid that opens it when the motors at temp... i would have put it back right, except like the idiot i am, i removed that soliniod months ago /forums/images/graemlins/smirk.gif.

    as soon as i pulled the vac off the EGR, the motor purrrred and i was able to turn down the idle... now she doesn't diesel or stall anymore /forums/images/graemlins/thumb.gif..

    if you have an EGR then i'd check that...

    i bet there are tons of us that have ripped off the smog stuff and hooked this thing up wrong...

    good luck
     
  9. Goober

    Goober 1/2 ton status

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    Re: Q-Jet Idle GREMLIN!!!!

    [ QUOTE ]
    When I cover the top of the carb with my hand when the truck is idling, the idle bumps up and smooths out

    [/ QUOTE ]


    That's the ol' shadetree mechanic way of checking for a vacuum leak. Guess what, you have one. /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif

    Since it started acting funny in a short period of time, I would guess that something like the diaphragm in the EGR valve, a baseplate gasket or an intake gasket are to blame.

    You should be able to find it, sounds like it's a pretty good leak.
     
  10. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Re: Q-Jet Idle GREMLIN!!!!

    See my update at the top...... /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif
     

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