Engine Vibration May Not Be Due To An Improperly Tuned Engine

When engine vibration is noticeable at idle, especially with 4-cylinder, odd-fire V6 and diesel engines, it is most likely a sign that the mounts are worn or completely broken. These vibrations tend to worsen when the A/C compressor is engaged. 

Over time, the rubber portion of a mount will deteriorate and often separate from the mounting plates, or crack and deform. The result is excessive vibration. Many late-model vehicles use hydraulic liquid–filled mounts to minimize NVH (Noise, Vibration and Harshness). The liquid is contained in the hollow cavity inside the mount. As the part ages, leaks can occur causing the mount to deflate and lose its ability to dampen vibrations. It can also affect other related parts on the vehicle.

Always replace hydraulic mounts with a new hydraulic mount when offered in order to maintain the original dampening characteristics that were designed for the vehicle. On high mileage vehicles, replacing all the mounts at the same time will help eliminate annoying vibrations and reduce the risk of other mounts failing shortly after the original repair. 

As little as a 1/4” misalignment of a sagging or twisted mount can cause the CV joint to be off line by 1” or more, adding stress to the drive train.

“Active” motor mounts incorporate hydraulics, along with a vacuum pump or electronic sensor to change the dampening characteristics. 

Active mounts are designed to be fairly elastic during idle and then stiffen up under higher engine RPMs and loads to absorb engine vibration. Late-model applications that currently have integrated active mounts into their vehicles are Acura, Honda, Hyundai, Kia, Infiniti, Lexus, Nissan and Toyota.