I haven't done any major work to the car. most recent work was an oil change 2000 miles ago, and plugs and wires 5000 ago. I don't believe its missing, the idle is smooth when in neutral or park. It also makes a loud rattling noise when it shakes... I'll check out the engine and trans mounts, but If it was an engine mount wouldn't it shake in neutral also?.. Lol Aetos, I wish It sounded like a big cam, I'd just keep running it!