I have a 2003 ranger and have had ongoing problems with misfire cylinder six and have had three different mechanics diagnose the problem as a bad ground. I have replaced all plugs, wires, coil pack, injectors and am constantly pulling the plug on cylinder six, cleaning and often replacing, I also disconnect the battery so it resets the check engine light and it runs fine for about 100 miles and starts running rough again and on goes the check engine light. I have 134000 miles and have maintained it since new, I need help please, is there some magical solution and if so please help! Thank you

 

Is the plug fouled. Picture of bad plug would help

 

When I pulled the plug it had what appears to be rusty looking on the threads but the top of the plug looked okay. Also I have had a burn mark on the plug wire which leads me to believe that I have some kind of ground problem. I have some arc marks on the edge of the manifold closest to the plug wire

 

If you had a ground problem it wouldn't be just #6 giving you trouble. From your description almost sounds like an exhaust leak destroying your plug wire.

 

There are arc marks on the manifold closest to cylinder six and that is nearest the plug wire that has marks. Also the threads on plug look almost like rust on them