I don't have a Ranger, but a guy I work with does. (I drive an Explorer.) It is an early 90's model I believe and has a 4 cylinder engine. He asked me if I knew if it had 8 spark plugs or not. He says he knows he saw 8, 4 you can get to and change and 4 you cannot. Is he right? Why are they there? All I could guess is that it is for some emissions control. Do they fire on the exhaust stroke or something to make sure all of the fuel gets burnt? That's what I told him my guess was.