I have a 2000 Jeep Grand Cherokee limited ed. with a 4.7 Liter 287ci v8. Recently my camshaft sensor failed so it was replaced along with my crankshaft sensor (mis-diagnosis) The Jeep ran perfect for about 500 miles after which, I started to notice a loud knocking sound similar to a back fire coming from the engine compartment. This is ONLY audible at speeds greater than 60mph during accelleration. At first I thought I had picked up some bad gasoline. I flushed the system with additive and tried using premium gasoline. No change. I found the spark plugs to be extremely worn so I replaced them with .40 gap autolite premiums. Acceleration through lower RPMs is drastically improved but no change on the knock/back fire sound at speeds over 60mph during acceleration. I have read diagnosis regarding the replacement of a "knock sensor." Can anyone provide advise on this fix based on the symptoms I have described?