Rumbling issue when JGC is idling or in neutral
Hello all, My JGC is 2 wd, inline 6, 165k miles. I have noticed that over the last few months my JGC is rumbling/shaking when I am parked with the engine running in drive or in neutral sitting stationary. Someone made mention that their could be carbon buildup around my throttle body plate so I completely cleaned that but also noticed the round gasket that goes between my throttle body assembly and air intake body is broken and I need to replace it (wasnt sure if that could be the culprit) Someone had mentioned it could be a damaged motor mount but I have no idea where it is located or what it looks like. I am not receiving any check engine lights. I also noticed today that when I started my car to go to work it was making a grinding noice and after a few of my car people looked at it they believe the bearings in my serpentine belt tensioner is on its way out as they said it looked like it was vibrating more than it should be, today was the first time it ever made any kind of grinding noise. My engine idles around 650-700 RPM when warm but around 1000 at startup and there is usually less rumbling/shaking at the higher idle RPM's
Any help or advice would be greatly appreciated.
99 Jeep Grand Cherokee Laredo Inline 6