Weird problem missing engine

[Stangesokning]

I have a 2001 Excursion 7,3 and i am having some issues with the engine missing/hesitating. I can feel the miss at idle and between 1200-1600 RPM.( It`s worst when it`s cold, getting better when getting warmer) It is doing this almost all the time, exept when the fueltank is under 1/4(and lower). When it`s under it runs like it should, barely notecing the miss.

I think it has something to do with the fuel supply but not sure. I also have 2 codes P0671 and P0683. Would these 2 have something to do with this problem?

Any suggestions would be very helpful.



Svenn