I have a 99 Ford Expedition that started running rough, checked the codes because it is showing check engine soon light, shows code for spark plug 4, took wire off put back on and erased the code

firebird338 can I just replace that spark plug? I know its not the best thing to do but right now I cant afford to replace all 8

Yes you can but also maybe the spark plug wire but you can try the plug first and if it does it again replace wire. Before replacing plug remove and take a good look at it if does not look that bad try cleaning and regapp plug.

i have no clue how to do that regapping thing. I either have to pay to have someone else do it or something I am able to do myself. The spark plug itself is only 5 bucks and maybe they will be nice to me at Oreillys and put it in for me? lol

If you are going to put in a new one most likely the gap has been preset from factory. Just recommended gaping if you were thinking about trying to reuse the old plug. The guy at the parts store can tell you if the plug has the correct gap already.

the man at the auto store was a little crabby when I didnt buy all 8. Thank you for the response.

Those guys at the parts store have no idea how to Work on vehicles all they know is how to sale parts most of them any way.