After several times to the dealer and no luck getting rid of this rattle, finally they found the problem. Replaced the motor mounts, sound is finally gone.

 

Where/what did the rattle sound like when you were in the car?

 

When it started I really couldn't isolate where it was coming from, it always sounded to me like it was coming from under the car by the drivers wheel well. The sound sounded as if something was loose and more a knocking sound than a rattle could only hear it driving 40 or under over moderate bumps. It progressivelly got worse to the point that you would hear the knocking when you started up the car or even when you would close the drivers door and of course over bumps the sound was more frequent and louder.

 

motor mount?! wow...interesting.

 

I had to get my throttle cable tightened, because at 3500 RPM's , I would hear a rattle from the engine compartment all the time. Park Ave came to the rescue!