2003 Expedition
I've had a problem twice in the past 2 days where I'm driving (doesn't matter what speed) and I go to let off the gas pedal and the engine stays revved. Yesterday I was driving about 30mph (1800rpm or so) went to let off, and it felt like the cruise control was on--engine stayed at 1800rpm and car kept going. Happened again this morning going about 60mph (~2200rpm). It's not completely stuck, as I can still make the engine rev higher, but it just never came back down below the point it was at (1800 or 2200rpm).

The past couple days have been about 5-10F outside (I have't driven this vehicle before in this cold of weather). So is it possible that it's getting frozen? Should I take it somewhere or is this something I can remedy myself?

Both times, I turned off the heat, stopped the engine, let it sit for a minute or two, then started it back up and it didn't happen anymore during that driving "session".

Thanks a million to anyone who can maybe shed some light on this for me!