Did you try what I recommended earlier? Pulling all the plugs and listening carefully to it being spun by the starter?

Or, a variation on this test would be to start the car, drive it up to a long hill, and then turn off the ignition (don't lock up the steering wheel). Then let the clutch out and let the car spin the engine up to RPM. Listen carefully, and see if you still get the vibration - at least then you know it's something definitely mechanical (versus ignition and fuel injection).

Another thing - if it's crank / clutch related, it will change when you engage the transmission and wheels. The rotating mass of the drivetrain will help to reduce vibrations. Does it change when you engage the clutch?

-Wayne

Thanks for all the thoughtful replies. I knew you guys would be relentless until we get to the bottom of this.

Wayne, I have not tried to feel the vibration during cranking. I will try that tonight. I am not sure that it will be enough rpms to really feel it, but I will give it a try. The vibration seems most noticeable at around 2,500 rpms, particularly in third gear. But I believe that is just because of the unique comination of load at that spot. It is absolutely present in all gears while driving, and in neutral sitting still.

And Warren, yes, it is progressive and seems to be most pronounced in the mid-rpm ranges. As stated above, it seems to be most noticeable around 2,500 and almost seems to become less noticeable at higher rpms. But, while the vibration is less noticeable, the power hindrance still seems apparent at those high rpms. It is also less noticeable at idle and low (below 1,500 rpms). At 2,500 rpms in second or third gear, the "harmonic" it creates is almost something you can hear, as well as feel!!

Dang, I wish one of you were here in KC. To bad there is actually no reason whatsoever most people would ever come here on purpose! I just know that if some of the crew who have been responding here could sit in the driver's seat and rev it, they would get a clear idea of what is going on.

Thanks for all your thoughts.

JA

Maybe more than one rod is (very) slightly bent/twisted - like two on the same bank?

WAG ALERT :)

Wouldn't a bent rod (stroke now doesn't match other rods) affect both the effective combustion chamber size in that cylinder (creating power loss / fuel mixture problems) as well as cause rotational balance problems (creating harmonic vibration thru RPM range) ?

YEAH!! WHAT HE SAID!