I have a 1991 Jaguar xjs v12 coupe. I was getting water on my drivers side floor. I lifted the carpet & found a whole in the middle of the floor with a threaded whole with a bolt missing. Do you know what it was for & why was there a threaded bolt there ? I also have a question why would my car pulsate with rpm ranging higher & then dropping & rising again after it has warmed up & then stop.