The front mount is liquid filled. When the car is idling the mount expands (or contracts, I don't remember which) to smooth out the feel of the car. When you accelerate the mount deflates. I cannot tell one way or the other. You supposedly get a stiffer ride with the solid mount. A lot of orgers here just replace the mount with solid mounts when the time comes due. Manual trannies have the solid mounts.... I think.

 

basically this in a nutshell. however you *NEED* to keep that sensor unplugged, unless you want to risk the fluid eventually leaking out, causing a short with the sensor, and having it fry your ECU and leave your car dead.

 

It is electrically controlled to expand and contract a jell like fluid to smooth out engine vibrations (in automatics) while driving. As the cars get older, the rubber cracks, the fluid leaks out, and sometimes the electric part develops a short. The 5th gens have a problem with a shorted mount blowing out the ECU. I either use a front mount from a manual transmission without the electric dampner, or run with it unplugged. It doesn't throw codes if the mount is unplugged. I prefer a more direct feel anyway.

 

^^^^^ I forgot about the ECU frying. I was told on the '98 they don't fry. Better off unplugged.