Interesting problem.

I've got an interesting problem land in my lap. I figured why not let a few other eyes take a look at it. It's a stock 2008 F150 5.4L. Customer had a used motor put in it 15,000Km ago. I am told the old motor lost oil pressure and ended up with rod knock. A couple weeks ago the customer decided they needed a new transmission. I have no clue why, couldn't get the proper story. The original transmission was rebuilt and installed, and ever since then the truck has been running like crap.

Customer mentioned it never ran that great, but this was even worse. The truck has been through multiple hands and now landed on my lap. Here's what I know has been done before the job got handed to me..

It had a cold air intake on it, that was removed and a stock air box installed with a new MAF sensor. Fuel tank was flushed, gas changed, Engine oil done, Factory reflash using OEM tooling, Exhaust back pressure tested - Less then 2 PSI loaded at 2500rpm.. Fuel pressure tested/matches pid readings... Cam/Crank correlation checked with a lab scope.. Evap disconnected, PCV disconnected.. I am sure there's been more..

Fuel trims are -20 to -25 at idle... It misfires and stutters getting off the line. It'll cruise ok, but falls on it's face under heavier load..

There were holes all ready drilled in the down pipes for checking back pressure so I removed the plugs and used my boroscope to look at the cats.. The sub-straight didn't look great, but didn't look damaged or melted either. I confirmed on the hoist loaded at 2500 RPM only 2 PSI back pressure.. I lifted the fuel injectors up and didn't find any of them leaking.. Spray patterns didn't look to bad from my make shift set up.. I checked part numbers and found they are 5C3E-DC.. From what I was able to find. These are for a 2007 and earlier... More digging showed the injectors for a 2008 are different. 7C3E-AB was the number I dug up. From what I could find flow rates are slightly different. So I down loaded some 2006 and 2007 tune files and did some comparisons.. They have different injector data. Being that it was late I figured why not.. Copied all of the injector data over from a 2007 and took the truck for a drive..

It was better but still felt like it had a misfire to it.. Got back to the shop and pulled the plugs... I figured someone before me would have done the basics.... Well nope.. I found 4 plugs loose.. 2 per bank.... The 2 on the drivers side were missing their ground electrode as well..

8 new plugs, 4 new coils to replace the ones contaminated by the loose spark plugs.. The truck still feels down on power and like it's got major flat spots.. It's not misfiring anymore thought. I can tell Bank 2 cat is toast.. Bank 1 is on it's way out.. I am trying to convince my self that it's a good idea to put new cat's in this thing.. but I am also not sure if I should be looking for any other odd ball crap because of the used motor swap..