I have a 1998 f250 and put a 5.8 FI engine that is out of a 1995 f150 , my problem is that the new motor runs very rough and smokes from burning excessive gas, do I need to change the EEC-IV ? the 1998 motor has a different firing order so I would assume that the injection firing order is different? please any body that can help me is greatly appreciated thank you -D-

 

What was ORIGINALLY in the '98?

You should have reused as MUCH of the original engine as you could: wiring harness, intake, distributor, computer...