Does anybody know what might cause a knocking coming from the back of the vehicle. It really does sound as if somebody was knocking on the trunk lid from the inside. The first time it happened when I just started the engine, just three knocks in quick succession. I shut it down and restarted, same thing. Then nothing for about two weeks and one morning it happened again when I started her up. This time I was able to determine it’s definitely originating at the rear of the vehicle. I immediately thought, "fuel pump" although there has so far not been any effect on the engine's preformance. This afternoon when I got home and shut down, I remained in the car for about five minutes reading something from work when I heard it again, without the electrical on. Although it didn’t sound as loud as before, it was four distinctive raps coming from the back end. It’s only happened about half a dozen times since late February, once while driving and rounding a turn (if that could mean anything). I plan on telling my dealer when I take it in for an oil change but I’d like to have some kind of idea what it is when I do. Other then this the car runs like a dream. Any ideas out there?