My truck is a 2004 5.4L fx4 with 298k miles on it. The original engine blew at 260k so I had it replaced with a re-manufactured engine. The transmission went out shortly after so I had it replaced with a re-manufactured as well. Around 6 months ago, engine started bucking at around 50-55 and check engine light came on. Code was cylinder 4 misfire. I replaced the coil pack and problem went away. A few week after that, the acceleration became very rough and threw a code indicating bank 2 sensor 1 was faulty. I replaced both passenger side o2 sensors and problem went away. Fast forward to now, check engine light is on again throwing codes P0305 (Cylinder 5 misfire), P0171/P0174 (Bank 1 and 2 system too lean), and P0320 (ignition/dist. engine speed input circuit). The only symptoms are similar to those when cylinder 4 was misfiring. I replaced the cylinder 5 coil pack and it is still throwing code P0305 along with the others. Any ideas on what could be causing all of these problems?

 

Did the re-manufacured engine include new fuel injectors, plugs, coils?

Just a general thing to do when chasing electrical codes -Check Grounds.

 

It did not come with new fuel injectors or coils. It did come with new plugs. I do use techron fuel system cleaner after every oil change.

 

If the injectors and coils have 298k miles on them do a tune up and change them out (all, not just the bad one). Im not about just throwing parts at it but at that mileage its hard to know what is still functioning 100% vs 85%. Check fuel pressure too. weak fuel pump or weak injectors = lean condition code. Lean condition = weak idle = engine speed code (lower RPM)???

Im just making assumptions so hopefully someone with first hand knowledge on this problem can better pinpoint the issue.

 

Can the injectors be cleaned instead of replaced? It seems that if an injector is clogged or dirty, a thorough cleaning would be sufficient. I've seen some cleaning systems that used compressed air to clean injectors.