so yet another post by me about the car i bought. it has a slight rough idle when its in park, but when i put the car in reverse, whether im moving or not, the car shakes quite a bit. its never stalled out but its a very noticeable shake. any idea what is causing this?

 

Idle speed could be too low but more than likely a motor mount is collapsed or torn. Check them all but especially the one by the radiator and the one by the firewall. Engine will move some in a twisting motion when you put the car in either forward or reverse gear and engine vibration transfer to the body is aggravated by a damaged mount.

 

My CX5 has done a similar thing maybe 4 or 5 times in 56,000 miles, but I'm guessing it's not a motor mount. It's quite a violent vibration too; it stops when the car is shifted back to park again. I have yet to read about a similar situation on these boards.

 

listen to babyhuey. wont hurt to check the motor mounts.specially the one close to the firewall. that one is difficult to see. when the car is on reverse gear, the force of the engine falls on a different motor mount than when in drive, but the engine spins at the same rpm and in the same direction. on park, the engine is just spinning the converter. check the motor mounts. and for rough idle, check for vacuum leaks, bad pcv valve or a dirty egr valve.