I've looked around the forums quite a bit. I have not found anyone that has had the same issue. I have a 2000 Expedition with a 4.6, with 175,000 miles on it. What sticks out to me is, I only have the P0174 code, and everyone else seems to have that, AND the P0171 code. Lean on both banks! I have checked for vac leaks with a propane torch so far. Nothing found. I know it could be a bad fuel pump, clogged fuel filter, dirty or failed MAF or an EGR as well as injector failure. So I guess my question is, wouldn't any of those problems throw codes on BOTH banks? I don't have any misfire codes either. If that is the case, I am thinking maybe I have a bad injector on bank two? Maybe I'm jumping the gun asking the question, but has anyone else ever had just the P0174 code, and ONLY that code?

It starts fine. Runs good until it gets up to normal operating temp. Then it sounds to me, like it is backfiring through the intake manifold. But even when it doesn't sputter and backfire, it lacks power in my mind, for a V8. Some have said the misfires and backfires get worse under load. Mine get BETTER! If I stab the throttle to the floor it goes away. The problems occur at cruising speeds and light throttle. I have not done a fuel pressure test yet, and I did have to pull the fuel tank down to change a brake line, maybe I kinked a hose?? But wouldn't both banks be affected by that? I just find it odd, I only have one code the P0174, unless it's an injector on bank 2. Thoughts?

 

I had only a P0174 on our 2003 5.4L Expedition.
I think if a vacuum leak is severe such as the PCV hose with a hole in it both codes will get set.
If a problem is minor it might set one code and then after awhile the other will get set.
To get only one of the lean codes the problem would have to be on the exhaust side of the cylinders since the intake manifold would affect all the cylinders.
I think these codes get set based on the O2 sensor readings so the problem would be between the O2 sensor and the cylinder.
My problem was the exhaust pipe to manifold bolts were about a 1/2 turn loose allowing air to enter the exhaust stream and lean it out.

 

I just got this vehicle, so I only have 5 days of experience with it. It needed a new battery when I got it, so there were no codes. All I know about it is that it sat for a year before I got it. The owner passed away, so I can't ask him any questions. I dug through the glove box this morning and found a repair estimate. It indicated a bad coil pack, but it didn't say which one it was. I will look at the exhaust, but maybe I should figure out how to test the coil packs. Not sure if that code could be thrown due to a bad coil.

 

A bad coil would throw a code like P0304 for "Misfire on cylinder #4" and would allow gas to pass thru creating a rich condition.
Basic code readers are available for under $20 on Amazon that can also clear the codes.
A fuel pressure tester is available at Harbor Freight for under $20, too.
You may still have a misfire, it takes a lot of misfires to set a code.
A bluetooth OBD2 port adapter and an app like Forscan or Torque can get you misfire data to isolate down to a misfiring cylinder.
If you get a misfire code, swap the coil with another cylinder to see if the misfire moves.
If it sat for a year, like mine, the gas may be bad, replace the gas and run Seafoam thru it.

 

I do have a code reader. I've got a VAG Com, a handheld Innova, and one from AutoEnginuity, which in the past, I paid extra for the extended Ford code deal. The laptop with the software on it died. I need to look into getting software for the new laptop. I also have a Scan Gauge that will read and erase codes. I did fill the tank with fresh gas and threw in some Lucas injector cleaner. I do have Sea Foam on the shelf as well. I read somewhere here that the computer ignores the O2 sensors at wide open throttle. And the problem does go away at WOT. SO I think you have me looking in the right place. Ugh! I'm trying to move a 1500 sq ft shop at the moment, so I just haven't had the time to really look at this thing. It's not my first time under the hood of a car, but I know Fords can be really hard to diagnose! And I'm not in a position to throw parts at it until it works.