The only thing I would add to all of these great comments is to keep driving it until you feasibly can’t anymore and stay a member on here. I’m the original owner of a 2003 XLT 2WD with over 295,000 miles on it. Several years ago, wait no more like a decade ago it started idling rough and that’s when I found this Expedition Forum because someone had posted on here that while it was idling rough, run your fingers along the black rubber hose that goes to the back of the intake and if you feel a rough spot seal it up with your fingers and if the rough idling smooths out, a vacuum leak is the problem. Since then I have been a fan and a member of this site and all you awesome people!