low rpm engine vibration HELP...

[streetlethal]

Ok ive got a 2000 ford mustang with a 3.8 liter v6 has a bad vibration at low rpm particularly at 1000-2000 rpm... this is whats been replaced...
plugs...
wires...
coil....
filters...
injectors....
engine... TWICE....
its an automatic and has had issues with misfires but was cured with injectors...
i have been told the harmonic balancer can go bad on these but it looks to be a one piece balancer so im not too sure... Long lewis ford in birmingham alabama said they even dropped the exhaust to ensure the cats arent clogged... they said it had an internal harmonics problem (hence the 3rd engine swap) cmon the cars got 60,000 miles on it. its on its 3rd motor wich hasent fixed it yet and has been driven like a baby... Im a fairly well experienced mechanic but this one has got my brain in a tailspin... I read a lot where people have had this problem before but noone has seemed to have a way to fix it... please help... thanks i cant find anything in a TSB on this either.. im up for suggestions...

 

[Skymarshal]

I've never heard of such a problem before. If the engine was changed and the vibration continued, it's obviously not in the engine (unless the computer is defective and is causing it). Are all the engine mounts secure/ not broken? Does it only happen in gear? The tranny might have a problem. Any codes being thrown?

 

[streetlethal]

the balancer and the flywheel are the only 2 parts carried over from engine to engine. the engine does this regaurdless of gear. its an rpm specific vibration. motor mounts are fine no codes and even does it without the torque converter bolted up. has there been anyone previous incidents with balancers or flywheels on this? I just can't imagine the pcm causing a vibration like this... thanks

 

[Skymarshal]

I guess replace the balancer and flywheel since that's about all it could be. A machine shop might be able to balance the flywheel if it needs it.