Vibration at at low RPMS and in neutral?

[Floor guy]

Picked up a 84 944 n/a that needed an oil pan. After doing the pan and a long list of other issues I found, including a new head gasket, it has a vibration while sitting still. As soon as I increase the RPMS, it goes away. The balance shafts lined up perfectly with the marks on the cover. This is a automatic transmission car, my other car is a standard, and has less vibration at idle. As far as I can tell the car runs great other than that issue, but it needs tires and a alignment before I can put it through it paces. Any ideas?

[djnolan]

Similar problem here... Suspect the flex damper is out of round...

Plugs and a miss

[pfarah]

Or the motor mounts may have achieved their life expectancy... All the vibration (at idle) went away once I had them replaced.

[Jfrahm]

Yes this sounds like classic motor mount vibration.

[Floor guy]

Replaced one of the two engine mounts, other one was firm and had no leaks, may have miss judged it. Plugs and wires done when I couldn't start it with out a mist of fuel. Changed the fuel relay and cured that problem. Unless you guys have any other ideas to check? I will look at flex damper and order a new mount from here. Thanks for all the ideas!

[jtehfreaks]

I had the exact same vibration going on (I've got an automatic as well). It went away after I swapped out the motor mounts with new ones.

[944 Ecology]

The vibration caused by bad motor mounts is typically a shaking of the steering wheel which smoothes out above 1600 rpm.

The vibration caused by an imbalanced rubber damper (missing pieces of rubber) is typically around 3000 rpm.

The vibration caused by mistimed balance shafts is also around 3000 rpm, and mostly felt in the shift lever.

[djnolan]

My engine mounts measure OK but I could try listening with a stethescope.

This thread intrigues me, but still a lot of work for me:
Changing 944 engine mounts the easy way.

[9FF]

Originally Posted by Floor guy

...The balance shafts lined up perfectly with the marks on the cover. ...

The lower shaft gear can be 180 degrees out even with the marks lined up and this will cause vibration that goes away with higher rpm. Before you start looking elsewhere, double check the lower balance shaft alignment.

[plyhammer]

Typically it is the passenger side mount that fails first

[Grandad#3]

I don't know about the engine mounts in a 944 automatic trans car, but my 968 automatic takes a different more expensive OEM engine mount. A regular engine mount has more engine vibration. URO mounts are a waist of time.

Cheers,
Larry

[jtehfreaks]

The 944 motor mounts are no different between the manual and automatic versions of the car; same part number and everything.

[djnolan]

Listening with a stethescope the noise I have is detectable from the top of bell housing and is not coming from the engine mount. This is at idle in drive on an automatic car.

[djnolan]

Could the flex damper spacing adjustment be the problem? Can this adjustment be checked and made with the transmission and torque tube installed?

[akron]

Originally Posted by 9FF

The lower shaft gear can be 180 degrees out even with the marks lined up and this will cause vibration that goes away with higher rpm. Before you start looking elsewhere, double check the lower balance shaft alignment.

I have the same issue and it is not terrible. But how would you tell if the balance shaft is 180° out?

[9FF]

Originally Posted by 9FF

The lower shaft gear can be 180 degrees out even with the marks lined up and this will cause vibration that goes away with higher rpm. Before you start looking elsewhere, double check the lower balance shaft alignment.

Originally Posted by akron

I have the same issue and it is not terrible. But how would you tell if the balance shaft is 180° out?

I should clarify, it is easy to get the lower balance shaft 180 degrees out if you haven’t done the job before. You would swear it looks correct with the marks all lined up but they are actually off. If you follow the manual and line up everything exactly as it says, you should be fine.