rough idle help!

[1991explorerEB]

just recently i started my 1991 explorer and usually when i first start it, it jumps to about 1500 rpms then drops to 1000 and runs fine, and sounds good, but this time when i started it it only went to about 1100 rpms and then idled real funny. if i shut it off and restart it, then it goes back to normal. and if i dont restart it and drive it with the funny idle i get terrible gas milage. any ideas?

 

[MrShorty]

Nothing specific, but I'd probably start with a few basic diagnostics: Pull codes (even if the CEL isn't on, check fuel pressure, and check for vacuum leaks.