last night when i got off the interstate and stop, my truck was idling very rough and was clacking real loud. drove about 1/4mi to next light and it was still doing it. drove about three miles more and when i stopped,, it was normal agian? it did this once before a coulpe months ago, it had a "bad plug" feel to it. i didnt check for a code but doubt it threw one, will check this a. m.