RevGTO

iTrader: (12)

A friend had his 01 Formula in my buddy's shop today. Car is M6, lid and catback only, 91k. His engine idles roughly, and develops a pronounced vibration @ 1200-1300 rpm in neutral that gradually smooths out as the rpms increase. It's enough to shake the steering wheel and other interior pieces in the affected rpm range.

A tech checked the injectors and scanned for misfires. Injectors were all in spec and there were zero misfires in that rpm range. No misfire codes, either. Plugs and wires are new. No unusual noises or anything.

The car seems to pulll out and drive normally with no loss of power, although the engine seems a little rough.

The tech feels it is an imbalance in the rotating assembly somewhere between the harmonic balancer and the flywheel. He doubts that it's the flywheel and says that if it was, the vibration would continue up the rpm band. LUK clutch is fairly new.

Any tips or help from your experience would be appreciated. He's pretty frustrated.

DaddySS

fix the rough idle first, then see what you have

RevGTO

iTrader: (12)

The rough idle isn't a distinct symptom from the vibration - it's an aspect of the same thing.

up2nuthingud

iTrader: (18)

motor mounts maybe shot?

99RedTa6spd

my 99 with 90k does the same thing..... my shifter and steering wheel shake bad at that rpm range.....

6.0 silverado

iTrader: (2)

Anyone figure this out? My car also vibrates just off idle and smooths out a little at higher rpms. It idles smooth as butter, but the off-idle vibration is driving me nuts

King Nothing

iTrader: (9)

yeah mine is doing it also, but i have 160K on it so i'm used to it now with my exhaust lol

6.0 silverado

iTrader: (2)

does anyone think a fluid damper under-drive pulley would help anything? Has anyone tried it?

LS1BLKSS

iTrader: (36)

put some poly motor mounts

6.0 silverado

iTrader: (2)

I have prothane motor/tranny/TA. I thinking of removing the tranny mount for a stocker to see if it will help.

Johnnystock

iTrader: (6)

Dont do this, I have poly motor/tranny mounts and no vibration at all. I know I had a misfire and would make the car shake bad and run weaker; One wire wasnt fully popped in...I would re-check that honestly before going further.

What plugs he is using by the way?

6.0 silverado

iTrader: (2)

I don't have a miss. The car still runs strong, idles smooth and there is no CEL. Maybe I'll start looking at the flywheel/ pressure plate or the accessories. I believe the vibration has been there for quite some time, but the prothane mounts made it more pronounced.