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  • 4.2L ENGINE KNOCKING NOISE

    I HAVE AN 88 SARAHA WITH ONLY 112K MILES. THERE IS A MYSTERIOUS KNOCKING NOISE. WE HAVE CHECKED THE BEARINGS AND THOSE SEEM TO BE FINE. IT ALMOST SOUNDS LIKE A FUEL PUMP BUT...?
    IVE ALSO NOTICED THIS SAME NOISE..TO A LESSER DEGREE.. IN ALOT OF NEWER 6CYLS. IS THERE ANYONE WHO COULD POSS. SHED SOME LITE ON THIS THANK YOU!

  • #2
    I am as curious as you are. I have a 92 4.0 that sounds like a deisel when ideling. I been told it is in the piston area either slap or comming from the wrist pins. I have had 3 differant mech look & listen all are unable to pin point the noise but all have eliminated the rods & timming chain & lifters. Not much left.

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    • #3
      My 4.2 used to make noises too. Check the:
      Cat to see if it's rubbing on the skidplate or not, fuel lines not connected to a clamp somewhere, and exhaust hangers broken.

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      • #4
        I have the same problem with mine (89 4.2L) I am thinking I have some valve lash in the valve train up top. It seems to lessen when I take it from a heavy load to a moderate load. I will admit that I was told a long time ago that for some strange reason all 6 cylinder engines seem to a tapping or knocking sound in them. Dunno why that is but I have found it to be true in all the 6 bangers I have driven. I don't reallt worry about mine too much. I have plans to get another 4.2 and tranny and do a ground up rebuild and build up (add a little ooomph into it). Once that is complete we'll see if it is a 6 cyl trait or not.

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