I have a 2006 ford F150. Has high miles but motor seems to run good except i cant figure out why sometimes it starts to sputter. it has done it since i got it and gets worse. Whats weird is had to put a new fuel pump on and it fixed the sputter for about a week. The code says miss fire on cylinder 5 and it says my cats are bad. Then I go get the cats tested the guy says they are fine. So then later i just change one coil pack on the 5th cylinder and it fixed it again for only about a week. It seems to have certian speeds when it does it. Probly around 50 miles an hour when it shifts into the next gear and if i keep it reved low. or if i really get on it, it lags like its not getting fuel or its missing and my check engine light flashes. I changed the fuel pump module and it didnt change anything either. I just cant explain it. Its weird and even guys who work on fords all the time can't tell me. They just give me a list what it could be. I thought maybe i just got bad fuel pump or something or just spark plugs. but idk i dont want to spend the money for spark plugs if that aint it. they were changed 2 years ago. please help?