A harmonic balancer will not cause a vibration that severe. If it did, it would've probably broken the crankshaft years ago. Also, any check engine light? If so, scan comp and send me the codes. (a faulty balancer would get worse at higher engine speeds, not just sitting idle. that in itself eliminates that possibility)

Check for a misfire by doing a drop test on each cylinder.

Answered by Ernest Clark (expert)
1,762 answers provided

Hey Ernest Clark i wanted to add a little to your answer.If it's just a vibration and not a miss fire then you most likely have a bad engine mount the most common one that colasp's and tear's is the upper one right by your coolant bottle where you would add coolant.Also is the vibration a lot worse in drive compared to park?You could also have a bad lower transmission mount.Those are the two most common cause's for a vibration if that's all you have and not a miss fire.

Answered by saturntech9 (expert)
23,156 answers provided

Thanks for the help saturntech. Most times it's pretty hard diagnosing symptoms that I can't see/test for myself

Answered by Ernest Clark (expert)
1,762 answers provided

The engine doesn't misfire at all, and the check engine light never comes on. I don't notice much vibration while driving, and it definately doesn't get worse at higher speeds. The vibration occurs when the car is in drive, but stopped (such as traffic lights). So if it's an engine and/or transmission mount, am I looking at a huge repair cost? Thanks for your help.

Response from starrkat
1 question asked

The mount's themselves are pretty cheap the most common one to go bad is the upper one right by your valve cover.That mount is only about 30 and with a floor jack,piece of wood,15mm socket extension rachet 7mm socket and vise grip's sometimes needed.The first thing is to see if you need the mount.If you could send me a pic of the mount the side of it facing your coolant bottle i can try to see from the pic if it's bad.

Answered by saturntech9 (expert)
23,156 answers provided