Hi Everyone,
Im working on my 2013 F450 SD . Has a 6.8 v10 Gas engine in it. I had an issue last month and ended up replacing the long block in it . I normally use OEM , but Ford didn't have an engine in stock for it, so I went with a Jasper Motor. Well, I got it put in , started, bled, and running, However an interesting development happened that has me scratching my head. Under Load it developed a misfire that thru diag I have determined that it isn't coils, boots, plugs, or injectors. Its weird. Fuel trims go full rich when the misfire occurs on bank 1 only. Once I take my foot out of it and let it idle for a minute, it comes back and runs fine. So to clarify, Misfire under load, then goes away at idle. Fuel trims return to normal too. I replaced coils, boots, plugs, and injectors all at the time I installed the new motor. I verified I have good pulse to the injectors as well as the coils. Verified spark present at idle and when loaded in the shop , but unable to confirm when driving.
Ive seen these motors have harness and ecm issues losing ground under extreme load where pulse width is increased, however, they were consistent, not under one condition or another. Ive also been toying with the idea that the cam gear may be wrong year and causing issue under load when timing retards. Thoughts? HELP?!?!?!?!


Related Test Data
P0300 Random Misfire Detected
P0301 Cylinder 1 misfire
P0302 Cylinder 2 Misfire
P0306 Cylinder 6 Misfire
New Plugs, Motorcraft, New Coils and boots, Motorcraft, Injectors, MotorCraft, New Engine Jasper Engines.

 

You made sure the spark plug was gap correctly? Check the ground on the block, next to the starter.

 

Fuel pressure? I notice it's misfiring at the front, on 3 cylinders, which surprised me. I figured it was just one cylinder until I got down to the codes.