I did a search before posting this, no hits. The '99RX has had a rattle in the right rear ever since I got it in '09, and when my radio antenna went belly up several weeks ago, I thought it would be an opportunity to find the culprit, because I knew I would have to take apart that right rear and spare tire assembly to get to the antenna motor. So, I did that job, and the new antenna works great, and I also insulated any wires or cables that could have the possibility of causing a rattle from any kind of vibration. So on a long road trip this weekend, the rattle was still there, and I was able to have my wife drive, and I crawled in the back with the right rear seat back down, and was able to isolate the rattle in the trim that surrounds the right rear luggage window. So I gotta get that thing off, not sure how to best do it without breaking something, hopefully it will just pop off with careful prying. Has anyone else had this issue, and/or removed this right rear plastic trim from around the rear luggage window? Any experiences will be appreciated!

 

Going by memory here:
There is a bar with screws and the rest is plastic snaps. Check for loose screw(s) and gently use your palm to press in the plastic.

As you mentioned the antenna motor and cable is there. If the motor is not secured (on rubber mounting) and the the foam on the antenna wire is missing, they can create a rattle.

Salim

 

Press something that vibrates against the panel. Maybe it will cause the rattle to occur.
I did that recently to isolate an exhaust rattle.