RE: Misfire spark plug #3
I have a 1997 Ford Explorer Sport 4x4 that had #6 misfire code. The plug looked fine, but changing it resolved the problem. I purchased the SCAN tool and erased the code. It has never returned.
Your Sport should perform badly (running on 5 cylinders) if indeed that #3 plug is not firing. Are you sure you have the plug wire fully conneted on the plug and at the distrubutor? It can fool you sometimes as the fit can be misleading to have full engagement. You may have a gap at one end or the other and it will fire fine most all the time, but when under a heavy load, it may misfire for a few beats, store the code and then go back to running normal!