April 20, 20111st let me say I am not a Ford owner as I own and prefer another brand. That is why I only have the couple posts since registering a few years ago. No offense meant as Ford trucks are good quality they just don`t appeal to me. However, my Brother has a Ford truck and that is why I came here originally.
I registered here once to get an answer when I was working on his truck. Recently he had another issue pop up and I used this site among others to try and correct the issue. I figured people were nice enough to me when I asked for help before so I decided to come back and post this to maybe save someone else a headache like I recently had with his truck. Trying to return the favor.
2006 F250 SD 5.4L
Truck started to breakdown and stutter when on the highway around 55 +/- when OD was engaged and also any time a load started to build( on engine )that would have it almost ready to shift. The issue went away as soon as it shifted. No CEL or anything and it almost felt like the trans slipping and/or the TC going. It felt a lot like the common bad plug(s) or one or more coil packs were going too but that usually trips a CEL from what I have seen and no CEL was tripped.
I have a scan tool and checked anyway but no codes. So it seemed to be tranny related( it really banged when it was doing it ). As said, it was at a certain speed mainly or when you got it to a certain point with a load( on engine )that would have it almost ready to shift. I had suggested taking it to a shop or the dealer to find out what was going on when it finally tripped the CEL. I thought for sure I was going to see P030# but to my surprise I saw...
Code P0174 - System Too Lean(Bank 2)
A search here and on some other Ford forums, as well as an internet search, showed this to be a pretty common issue for the trucks and Expedition SUV`s with the 5.4L. Very common for code P0171 - System Too Lean(Bank 1)to be with it although my Brother`s truck did not have that code. The search results everywhere almost universally attributed those codes to one of 3 things...
1 - dirty/failed MAF
2 - vacuum leak( probably the PCV line )
3 - fuel filter
This made a lot of sense to me as I have had a truck before( GM )that had the MAF fouled by an oiled air filter and it had the same sort of driveability issues. So we looked for any kind of problems with the vacuum lines( none we could find ), changed the fuel filter( kudos to Ford for giving you a filter on the frame rail you can actually change vs. burying it inside the tank ), and then I pulled the MAF and cleaned it. I was sure it was the MAF was either dirty/fouled or gone bad.
I used the scan tool and cleared the code when done and we took the truck for a ride. It seemed to run good for a couple minutes and I was feeling good saving my Brother all that money at a shop but then bang bang bang, stutter stutter stutter, and the CEL came back! AW CRAP!
At that point I suggested we take it to the local dealer as they have the equipment to narrow it down more that my handheld scanner couldn`t do. Plus they could do a smoke test for the vacuum leak. We dropped it off and I told them what we had done and they thought we had done right to that point.
Got the call the truck was fixed. Turns out it was a bad coil. Makes no sense but that is what the issue was. They changed the coil and the plug in the bad cylinder( their machine showed it as bad )and the issue is gone. No codes you would associate with a coil/plug either. Just the P0174.
So all this long winded rambling is to let you know if the 3 common fixes above don`t correct P0174 start checking coils and plugs. Oh, and the dealer said they have also seen a small intake manifold leak cause that code as well. Hope this helps someone out? I know I looked online for a couple hours and read post after post and never saw anything but the 3 things mentioend above as the probable reason(s). Never once a coil and/or plug issue nor that the intake could be leaking and causing it.
I hate modern computer controlled vehicles. Give me a carb, a distributor, and an engine you can actually see to get to and work on anyday over this modern crap with the 16 million vacuum lines, sensors, and other emmissions bs.
Have a good day guys.