Every once in a while when I turn the key to start my car, it feels like the engine shifts or something, and the car kinda jerks back when the engine starts up. Is this the sign of a bad motor mount? My Z is a '99, and I've never replaced the motor mounts.

I put on the poly upper mount add-on a few years ago, and that's about it......never touched the lower mount before. Anyone have any ideas?

I had the EXACT same problem, and a new lower and uper mount later all is well

Hopefully replacing the lower mount will do it. Thanks for the info.