I'm fixing up an 1989 accord for my son...we've got the engine running but when we put the car in Reverse the motor jumps...is this a sign of worn motor mounts?

 

Do this both in reverse and drive.

with the breaks on, hood up, put in gear and see how much it moves. If it moves more then 1/2 inch in drive or reverse then its Engine/trany mounts.

You should do a visual inspection. See which ones look bad, and if not sure then just replace them all.

Good luck