Need some help figuring out an engine miss

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  • bill32
    230 Tornado
    • Jan 14, 2010
    • 6

    Need some help figuring out an engine miss

    1979 Wagoneer, 360 motor, holly 4 brl, motor has been rebuilt at some time recently and carb appears to be new (which the previous owner said he had bought. He converted it from 2 brl, installing Edlebrock intake and the carb. I Just purchased the vehicle.

    The engine has a distinct miss at any speed, including idle. It appears that I am getting no or almost no power from #8 cylinder. I traced the miss to #8 by pulling the plug wires one at a time to check engine response when running. When I pull the plug were on # 8, it makes no change in engine idle or miss condition. Pulling plug wire on any other cylinder results in a noticeable decrease in idle speed and increased roughness.

    OK, so I checked distributor cap and rotor, which appear to be brand new, and they look fine, no cracks I could see, not carbon tracks, etc. Checked the plug wiring to make sure all wires are to correct cylinder. Plug wires appear to be new. Pulled #8 spark plug, which looks normal for a firing plug. Reconnected plug wire, held plug against the block while engine running and can see plug sparking consistantly. Next ran compression test on #8 cylinder, shows 150 PSI, which is right on specs.

    I am baffled. The cylinder has spark and compression, but appears not to be putting out any power.

    Anyone have suggestions as to what to check next?

    Thanks,
    Bill
  • FSJ Guy
    • Mar 20, 2005
    • 10061

    #2
    If the intake valve was not working AND stuck closed, it would show as having good compression, right? Maybe pull the valve cover and verify that the valvetrain is moving.

    Just an idea. I've never run into this problem.
    Ethan Brady
    1987 Grand Wagoneer, slightly longer than stock.

    www.bigscaryjeep.com

    Don't mess with me. I once killed a living hinge.

    Comment

    • Ristow
      • Jan 20, 2006
      • 17292

      #3
      or a busted exhaust valve spring. sucks the exhaust valve open on the intake stroke.
      Originally posted by Hankrod
      Ristows right.................again,


      Originally posted by Fasts79Chief
      ... like the little 'you know what's' that you are.


      Originally posted by Fasts79Chief
      I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!

      It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...

      Comment

      • amcboy
        232 I6
        • Jan 24, 2010
        • 68

        #4
        This is a good place to start!

        Assuming the mechanicals are good engines/cylinders don't fire for two reasons only:

        1. No fuel
        2. No spark

        So If you have spark there must be no or not enough fuel...


        Rag in the intake runner?
        Questions?
        Answers?

        amcboy


        '82 WT Cherokee
        '70 AMX (AMC power!)
        Max horsepower is at a single point and is called bar room horsepower

        Comment

        • Ristow
          • Jan 20, 2006
          • 17292

          #5
          i was working on pulling the head off when i found my problem. same thing, good compression,clean plug. no apparent reason for the miss.

          i've been tryin' to track down a miss for a week.compression test came up good.pulled the valve covers,all the rockers were good,and had full lift.pulled the intake,found a lot of oil on the intake valves,thought maybe gummed up valves.i always suspected the cast iron square bore maniflod i had on was leaking from the
          Originally posted by Hankrod
          Ristows right.................again,


          Originally posted by Fasts79Chief
          ... like the little 'you know what's' that you are.


          Originally posted by Fasts79Chief
          I LOVE how Ristow has stolen my comment about him ... "Quoted" it ... and made himself famous for being an ***hole to people. Hahahahahahahahahha!

          It's like you're unraveling a big cable-knit sweater that someone keeps knitting...and knitting...and knitting...and knitting...

          Comment

          • Hankrod
            Banned
            • Jun 22, 2005
            • 272

            #6
            Or a broken exhaust rocker arm. Hankrod

            Comment

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