I've done a pretty thorough archive search and haven't found a good answer yet.

I have a 98.5A41.8TQM with about 170K miles on it (owned since 29K). A couple of years ago the car started to exhibit a mild/moderate vibration in the engine when outside temp was below about 30 deg. F. Didn't matter if driving or sitting in garage, clutch engaged or not, engine hot or cold. Over time, it now seems like the vibration happens when it's really hot outside as well. If it is 45 to 75 outside, car runs like a sewing machine. Dead of winter or summer, vibration all the way up through the steering wheel. Had the car to 2 dealers and 3 independants, and they say that is just the way that engine is, but I know personally that the car was sewing machine all the time for the first 120K miles.

I have replaced snub and motor mounts. Made no difference. Don't know what else to inspect or check. Can I check any FI sensors with a multimeter?

Car has a number of original components, including all suspension, O2 sensor, fuel injectors, exhaust. I had APR 1.0 Bar chip installed at 51K miles. I know one of my outer tie rod ends is shot. My valve cover gasket is leaking quite handily. The strange thing is the Vibration's dependance on outside temperature.

The car has been so good to me over the last 9 years (longest I've ever owned a car, and best car I've ever owned) I can't be too upset, but I would love to resolve this issue. I've never spoken to any other 1.8T owners with a similar situation. Car pulls strong and idles steady at rest, just with a moderate vibration.

Great big thanks in advance to anyone that can steer me in the right direction.

Mark

 

What motor mounts did you use?


Are they installed correctly? I've seen the LS mm installed on the wrong side of the car, believe it or not: my Avant had some hambone in there before I bought it (4th owner).

Check the rear mounts (not just the front and snub) where everything comes together at the Torsen. Also make sure your hub bearings (where axles go through the upright) are good.

Beyond that, I can only surmise that you need a brightly lit thorough underbody inspaection by a qualified tech.

 

I purchased the sport motor mounts from Pure Motorsports and the slightly translucent red snub mount (can't remember specifics). I installed them myself last last summer, and the process went fairly smoothly. I don't recall the specifics but I did get some electronic help from an AWer. I'm pretty confident things were installed correctly. The unusual temperature dependant vibration didn't seem to improve at all. I have thought about the "transmission mounts", which are I believe what you are referring to the rear mounts, but haven't done them. From my recollection, they are substantially easier to install.

Hub bearings are new to me. Different from wheel bearings? I replaced my rear wheel bearings this summer, but the fronts are original. No resonance or ill grinding affects when touching the front springs during wheel spinning (how I usually check wheel bearings, in addition to the classic check for wheel play).

 

Does your outside temperature sensor monitoring the air temp properly? Is it detecting -38 degrees or anything that is clearly not the temperature?