I got so focused on the fact that the Vibration was occurring while driving that I missed that it would do the same thing while in Neutral standing still. My Vacuum Gauge read 18 steady at Idle but the Plug breakdown was occurring at High idle Speed.  Sometimes a fresh set of Eyes helps. My initial thought was the Output Shaft Bushing on transmission because there is some Play but not enough I guess the cause the Vibration..Anyway glad I did figure out what the Problem was in the End.

  

Mark, 
        Sometimes the most obvious thing is the hardest and last thing you look for. Glad it was so simple.



Frank/Rebop

Bristol, In ( by Elkhart) 

I don't have that Tool but a Induction Timing Light which I have would work. I went through the Plugs One at a Time. I found 2 Plugs #3 & #4 Cylinder that didn't look as clean as the Rest. I switched out those 2 Plugs and the Problem appears to be fixed. No more Vibration at high Idle and no Vibration when driving. Seems to be much more responsive too. So all my Time and Money spent looking for different Answers appears to have been fixed with $6.00 worth of 2 new Spark Plugs. If the Mechanic at the Shop I went to hadn't pointed out that there was a Vibration even at high Idle  without moving I would still be Scatching my Head. And that Advise was Free.

  

Lisle 19380 Spark Tester

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I  kind of wondered about that myself. I guess I could take an Extra Ignition Lead and Spark Plug and try One Cylinder at a Time and see if it makes a Difference unless You have a better Suggestion for Diagnosing?

  

Could it be that it is not firing on one cylinder completely and it levels out as the revs increase?

You are correct. Didn't think about that.

  

If I disconnect the Converter from Flex Plate can I run the Engine and perhaps better diagnose if the Problem is Engine or Transmission related? Is there any potential Problem doing this?     

Only trying to START the engine. You have the earlier F/M with the ring gear on the convertor housing don't you?

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If I disconnect the Converter from Flex Plate can I run the Engine and perhaps better diagnose if the Problem is Engine or Transmission related? Is there any potential Problem doing this?

  

If you did not reinstall it in the same position, then turning the converter might be worth a try.  If the flexplate has a heavy spot and the converter has a heavy spot and you get them lined up, it would probably be noticeable.  Mark them with paint or a marker so that you don't loose track of where they were in relation to one another.

The damper is fairly small and close to the crank centerline so there is less chance that it is the problem.  I don't know how you would test that besides installing another.


Lawrenceville, GA