So I have a 2006 SCrew f150 it had the 5.4 flex motor but the previous owner didn't believe in changing the oil. So I picked up a new 5.4 which turned out to be the newer design motor. I have read on this forum that this motor will just drop in and work. I have basically repalced all of the sensors with new but it is still running rough. It feels the same as the old motor before it died. It basically idles rough at about 650 rpm. It doesn't have enough power to properly shift the transmission so when you drive you get a trans failure message. The weird thing is no codes or check engine lights. We have compression tested the motor and checked about everything we could think of. I am thinking the ECU is bad but I am not sure how to have it tested and thanks to the PATS system I cannot just swap in a new one without a vistit to the dealer. Anyone have any ideas what to check next?

 

noone?

 

If the old owner never changed the oil I'm guessing you need fuel filters

 

I was thinking fuel pump but I guess a fuel filter is possible.