94 explorer makes noise and engine light

I have a 94 explorer I bought from a guy which checked out good when i bought it back in november. but now anytime I push the engine up to highway speed or up hills, it makes this noise like something spinning or bouncing around. then the check engine light comes on, but after driving about a mile it turns off. anybody know what its doing? Plus Im looking for a wiring diagram that shows what colors the horn wire is for my remote locks.