I have had a check engine light on for awhile and finally brought it in to autozone. He told me it was the gas cap. I had been told before that ford has had a problem with this. Is it as simple as replacing the cap or will this happen again if I do? Or is it really something else?

 

I'd start out by making sure you gas cap in on correctly, clearing the computer, and then see if the check engine light comes back on or not. The check engine light will come on if you start your truck with the gas cap off. If the light does come back on, simply replace your gas cap, clear the code, and you should be in good shape. (To clear the codes, just disconnect your negative battery terminal for a few minutes with your headlights on. After reconnecting, allow your truck to idle for about 5 to 10 minutes before driving it (as the computer needs to 'relearn' it's idle properties.)

 

Gas cap failures are rare.
I would have it properly diagnosed, rather that trying shot-gun a whole bunch of parts on the truck.

 

Do you know what the actual code is. I think that the code should be something like P0442 or P0455 or P0457.

Those are the ones that list possiable things that note a fuel cap problem ( loose or cross threaded ).

If you know the code, it is best to post it, and try to figure out what is wrong, rather then to take the verbal description that the guy provides on the problem.

Good luck