If you have access to one you need to do a buzz test and also check voltages koeo
Need more info as far as what was the truck doing prior to ficm swap, why was it swapped to begin with
Unfortunately, I have no access to anything that would scan or do a buzz test on a 6.0.
It was swapped because it wouldn't start when cold (40°). It would spit,fart, and sputter, but wouldn't start. If you plugged it for a few hours, it would would spit,fart and sputter like it was only trying to fire on 3 cyclinders. But longer you cranked it, it sounded like it was gradually starting to hit on more cylinders and eventually started.
When it did start, it ran very rough for 30 seconds. But after the 30 seconds, the thing ran like a raped ape. It would idle there just as smooth as smooth could be. Throttle respond was perfect.
Once the truck is warm, it will start right up until it gets cold again.
That's when I checked the ficm voltage, saw it dropped to 17 while cranking, I thought for sure the new ficm would take care of it.
With the new ficm, it still spits, farts, and sputters. But instead of sounding like its trying to start on 3 cylinders, it sounds like its trying to start on 5-6. Its better, but just won't start.
While cranking, before and after the new ficm, the smoke is black.