Engine/Transmission (1994 - 1998) strange engine vibration

[Hootguy]

I have been chasing an engine vibration for about a year now,,,it is noticable while in park or neutral,,,,it's not a constant vibration,,but more like a vibration short pause and vibration again,,some thing like 280 degrees of vibration in a 360 degree revolution,,any idea what it could be,,,we have checked the front damper which looks ok,,but it does have 500,000 KM's,,,we even went to the trouble of disconecting the torque converter from the engine to test,,vibration was still there... was wondering if the flywheel might do this,,,the engine oil has no metals in it,,so i doubt a rod or main bearing could cause this,,any ideas???

Dont really want to have the engine torn appart without knowing more,,

 

[budnate]

how does your front balancer look like? look close at the rubber, they do fail.

 

[Hootguy]

i did look at my damper,,,even took it off to check,,,looked ok,,but it does have 500,000 KM's on it... . can they get bad without the rubber comming out,,,

 

[budnate]

I was told when doing my KDP they tend to fail with age, I changed mine with a new one at 250K.

 

[kcv67]

What rpm do you feel the vibration in?

 

[DonFitzwater]

I had strange vibs in my early 98 12 valve. It had 175,000 miles on it so I just said what the hell and threw a new fluid dampr on it and the problem was no longer there. My balancer looked ok as far as the rubber goes but the out ring was moving rearward by itself.

 

[Hootguy]

Hi KCV,,the vibration starts at 1300 rpm's and seems to go from there,,,same frequency. . ,,and like i said,,it 's a vibration with a small pause every revolution it seems,,,so not a steady vibration,,i wonder if an accessory could be doing it,,or possibly the ring gear,,,would a faulty damper cause that type of not constant vibration???...

 

[ewcmr2]

Have you removed the serpentine belt to rule out all the accessories?
I once had a M3 with a mystery vibration. Turns out the motor mounts had deteriorated to the point where the engine sank in the chassis to allow the oil pan to contact the subframe mounted steering rack! Nothing wrong with engine, just two parts touching that shouldn't have been in contact.

 

[Hootguy]

Removing the belt will be my next test,,,,see what happens,,,dont think the injection pump could cause a vibration like that could it??

 

[KRStone]

Engine mounts?

There was an article in the TDR about the damper. I don't recall which issue.