My 99 Ford Escort will turn over with a weird sound, but won't start?

my car will turn over but won't start. the turning over sounds kind of weird, different than it sounds when the battery is dead. i think i had an idle air control valve before, because it would shudder and cut off when idling, but last night it started shuddering extremely bad and would cut off if I didn't rev the engine. While running it sounded almost like a diesel engine. I finally turned it off and now it won't start at all, although it does turn over with a kind of clunky, scratchy noise? I'm not sure how to describe it. Any ideas?