I have a Ranger, 4.0 which is probably the same thing as your Explorer. I had the same problem, opened the hood and figured it was my intake. And of course, with the cold weather the mice got intot he airbox and had started making a nest, thus clogging up my intake. Cleaned it out and now runs fine. Also depending on what year yours is the MAF cannot be cleaned so, just check out your intake system. Could be the issue, but keep an eye on your temp guage just incase it isnt.