My accords idles in part around 1000 rpm. After putting it into gear, the rpms drop to 600 and engine begins to vibrate. It vibrates at lights.

Does the idle need to adjusted? Could it be the Harmonic Balancer? How do you determine if your Harmonic Balancer is bad?

Any expertise answers are appreciated.

 

first check the IAC valve on the back of the intake manifold, its aluminum and has a black piece of plastic on it. the rough idle might be extra noticeable due to a bad rear motor mount. they are hydraulic and are controlled by a vacuum solenoid. if its bad you'll feel all kinds of vibration at a stop light.

to check these you start the car and then unplug electrical/vacuum connectors .

 

Agreed. The rear mount looks like a bear to change (I bought one 2 years ago and still haven't gotten around to putting it in). You could check the side mounts; the front mount (aka torque rod) is probably torn to heck but changing it won't get rid of your vibration.