2000 4.0 OHV knocking

Discussion in '4.0 Engine' started by Rfried20, Mar 16, 2018.

  1. Rfried20

    Rfried20 New Member

    I have a 2000 Ranger with the 4.0 ohv. It is making a knocking sound coming from the upper intake plenum. I replaced the upper intake gasket and orings. New plugs and wires. When I started it, it sounded a lot better but then progressively got back to what it was when I started. I have a video of it running but not sure if I can post it or how to. Any direction someone could point me in would be great. Thanks
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  3. OP

    Rfried20 New Member

    Ok so I did compression tests. They range from 110 to 135. Went down the line on the ignition coil, removing one plug wire at a time. When I removed the #5, the noise went away. So I found the location of the misfire. Next step is removing the valve cover and seeing what I can see. Ran out of daylight today. My “theory” is it has to be intake valve related for it to be making noise in the intake. Stethoscope on the exhaust manifold is quiet, but is also quiet on the valve cover.
  4. mhoward

    mhoward Member

    When you remove the spark plug wire on that cylinder, that kills the detonation in that cylinder and takes pressure off the piston and related parts. What you described sounds like a cracked piston skirt.
  5. OP

    Rfried20 New Member

    Actually, progress made. But a few corrections. It was actually the number 6 spark plug wire and the exhaust valve. The push rod was bent at a 45 degree angle and the lifter was broke. So the intake backfire was the exhaust pushing out the only valve that would open. All I have left is to hook up the exhaust manifold and change fluids. Then it’ll be ready to run again.
  6. mhoward

    mhoward Member

    Awesome! That doesn't sound too painful!

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