My daughter has one of these, and it's a cool little car with a DOHC 4-cylinder that has a lot of power. It also gets about 40mpg which is great. However, the thing vibrates when idling in gear and more so with the A/C on. She had the motor mounts replaced and we have had the belt tensioner replaced, but it still does it.
Any insights into why this happens? I tuned it up and it's running well once off-idle.