[s-cars] Harmonic Vibration?

[CyberPoet]

That harmonic vibration at 3200 - 3800 and reappearing at double that
(6500 RPM) is not necessarily from the engine unless you have isolated
it down to the engine. Any part connected to the engine area can be
induced to vibrate when it hits the right harmonic frequency (every
item has an inherent frequency; when the engine hits a specific RPM, it
causes whatever else to vibrate with it).

The first things to check are (in order, based on the KISS principle):
1. Engine Mounts -- if you're lucky, this is it.
2. Tranny mount(s).
3. Timing Belt/timing/tensioner.
4. Disconnect A/C, hydraulic pump, alternator and recheck for
vibration. Reattach if not basis.
5. Remove the oil filter and cut it open -- check for metal particles
(indicating a bearing has failed and metal is grinding - if yes, go
straight to step 9).

6. Have someone else run engine at 3500 RPM and work around it with a
stethoscope.
7. Front, rear cam, crank bearings from the outside.
8. Drop the oil pan, look for signs in the galley, slop in rod
bearings, etc. Remember the idea here is to find the problem with
minimum effort.
9. Yank the whole engine and tear down (goody, fun for the weekend...
do it in the living room just for shits and giggles).

Good Luck!
=-= Marc Glasgow
www.cyberpoet.net


TM Wrote:

> Has anyone experienced vibrations coming from the 2.2T engine in
> specific R=
> PM ranges?  My engine seems to vibrate b/t 3200 -3800 RPM
> (significantly) t=
> hen again after 6500 RPM (very slightly).  Runs really smoothly when
> it is =
> out of those ranges.    Happens in all the gears and in neutral (even
> happe=
> ns when the car is stopped and in gear with the clutch engaged.  I
> have che=
> cked all of the heat shields and the exhaust system - everything is
> tight. =
>  If it is a harmonic vibration, can it be fixed by tearing down the
> bottom =
> end of the engine and re-balancing everything (harmonic balancer,
> crankshaf=
> t, rods/pistons, and flywheel)?  i.e. leaving the top-end un-touched?
>
> Any input would be much appreciated.  Thanks.