Lately I'm hearing a knocking on my passenger side right near the battery, I'm pretty sure it's not from the engine, but I can't tell exactly where it's coming from. I hear it only when the car is on park or at drive, when i put it on N you don't hear it anymore. Another problem i dunno what's causing it, when im on park and the car is on, every 5 minutes or so my rpm drops all the way and goes back up to it's place.

 

My buddy had the same problem on his. It was his rusting exhaust. Maybe its possible?