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engine vibration/bad cold start manners??

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jms, Apr 12, 2002.

  1. jms

    jms 1/2 ton status Author

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    The 350 in my Jimmy has developed the shakes at idle, sounds like intermittent misses, particularly when it is cold. Specs are: recent vortec heads/intake, headers, Q-jet rebuilt last summer, Summit cap and 48kV coil a year ago, new summit wires after the heads went on. I've played a bit w/ idle and fast idle rpm - it takes a while for fast idle to kick in when cold, I typically have to help it along, because initially is sounds as if it were missing on two or more cylinders. Doesn't take long, maybe two minutes, until it's on fast idle, and then it's ok.
    Exhaust looks dark, so it seems to get enough fuel - maybe too much? Idle mixture screw is sealed on my carb, so I suppose there's not much I can do. Any suggestions? Oh yeah, EFE is disconnected for the moment, and that helped a bit, but not much.

    When warmed up, the engine still shakes a bit. I have the small balancer (original engine was a 305) - can anybody clue me in what the lifespan of a harmonic balancer is?

    Thanks for the input, michael
     
  2. joker89blazer

    joker89blazer 1/2 ton status

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    How good does the choke work? Engine needs richer mixture when cold. I would try spraying a little carb cleaner down the carb and see if it changes idle (do not want your head over carb when doing this,can be bad on hair if back fires). Fuel / air mixture needs can change a lot from a stock motor to a built motor. I built a motor that drove me crazy idling bad and backfiring through intake , carb worked fine on stock motor , larger carb fixed problem. hope this helps
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    The "missing" you're describing sounds more like the choke needs adjusting. It's normal for a cold engine to sound like it's cammed up until the choke plate opens. Once it opens the idle will smooth out and reach the high setting.

    Get ahold of Grim and he may be able to hepl you out....../forums/images/icons/smile.gif
     
  4. ntaj*ep

    ntaj*ep 1/2 ton status

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    You say this is a development, is this as of late, or have you been living with this for a while? You also stated that your carb. was rebuilt, by you or....? When I rebuild carbs. I always drill out the plugs for the mixture adjustment screws. So if a shop did the rebuild I would take it to them and have them adjust their rebuild. If you rebuilt it, its pretty easy to get the plugs out and adjust the mixture. Another thought, I would pull you spark plugs and assess the mixture each cylinder is reciving. I also reciently did the vortec head swap with carburator and have since had some intake gasket problems, maybe this is also the case with your issue. Hope some of this helps, if not all.
     
  5. jms

    jms 1/2 ton status Author

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    Canmore and joker89blazer, thanks for the pointer. I've been moving the choke blade manually while it was running, and when I close it all the way I can duplicate the condition even when the engine is warm. So I'll have to degree the choke - only problem I see there is that there's a notch on mine that locks it into one place, we'll see.

    ntaj*ep, thanks for the input, it's a recent development, it didn't do it initially after the head swap. I did the carb myself; I left the mixture screw alone. I'll take a look at the spark plugs, although I dread this now since I got the headers....
    With respect to the intake gasket: did you have to change it, or would re-torquing the intake bolts do any good?

    Anybody with an opininon on the harmonic balancer issue?
     
  6. ntaj*ep

    ntaj*ep 1/2 ton status

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    My main problem has been with the vally seal (rtv), But I've also noticed that coolant was disappering I would retorque the bolts and it would be fine, for a while. I would replace the gaskets and again it would be goog for a while. I've been thinking of calling Edelbrock and asking them about the manifold. I've also been thinking of putting a coolant pass through in the blanks at the rear of the manifold.....but?

    The headers and plugs.......suck a$$ I don't know what headers your running but I have some tri-ys and I haven't changed the plugs yet but I remember putting the heders on first, then the plugs. Dough! The problem your having almost sounds like it maybe in the carb. But I think the color of the plugs will tell the story.

    I think if your using the factory style balancer, and the rubber is not cracked it's fine. However the timing mark is cast in diffrent places, even for the same displacement motors, so be sure to time the motor accordingly. Hope this helps some.
     

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