rough idle

ok i start my truck itl stay running idles rough at 500, i can give it gas an will stay running, i floor it an revs up, but still rough all the way though. what could it be, any test i can do on any of the sensors? i thought it was the iacv ,replaced with a good used one,same, maf replaced 3 years ago, fp 2 years ago, i sent my comp off to a guy on ebay to get rbuilt, they said it tested good. before all this it ran fine, then the crank bolt backed out an the truck lost timing, no jumpin no damage that i could see. ive heard these trucks have tons of probs. any insight will help. thanks inadvanced, maybe send it off to avproecu? i think it might be the capacitor on the ec but idk what to do. really need my truck running.

my truck did that, and it ended up being the cap and rotor, have you changed that yet?...do you have raw gas smell from the exhaust? may be an injecter,...did you get it back in time right, maybe a tooth out,...just throwin things out there

sorry forgot to mention full tune up an havent smelt the exhaust, how would i know if injector?