Hello all, I have an 05 Endeavor limited and I absolutely love it, never any issues but I am experiencing something now. It sometimes taps in the engine rapidly, if I accelerate it taps faster and if I decelerate, it slows down. It's not all the time, maybe a couple times a month and of course it doesn't do it when I take it to a mechanic to have it checked out, they say if it isn't doing it when I bring it then there's nothing they can do and one guy said if it's not constant then it isn't a mechanical issue, not sure I believe that. Any ideas??