2003 Ford f250 7.3 no start

03 f250 7.3. If truck sits for several hours it will start run really rough for 15 to 30 seconds then dies will not restart till it sits for few hours. Oil change and few filter two weeks ago oil level is fine. I have unplugged the icp no change. Tinner nut on ipr is tight. I do have forscan not sure what i should be checking any help would be appreciated.