I was looking at my friends explorer sport the other day and noticed the tensioner is constantly "jumping around" I neaver noticed on his but on other cars usually I only notice it move when the ac compressor kicks on or off. HIs is constantly jumping around I'd say maybe 1/8 or 1/4 of an inch. Could this be the tensioner itself or a componet causing this. It only has about 50k if I remenber correctly.

I would say it's the tensioner itself.