Thought it was spark plugs...
 

Over the last week and a half, my truck has been "lurching" when coasting around 1250 RPM (40-55mph). If I turn off Overdrive, it immediately stops lurching, and if I accelerate, it also stops lurching. While the vehicle has lurched, the tachometer stayed around the 1250 mark, and had no easy visible changes.

My mechanic suggested changing my spark plugs (I definitely do need to, but goodness I hate the 5.4's). This morning, my check engine light came on. I was pretty excited to go into the shop and run the OBD2, that way I could tell which cylinder was having problems.

As it turns out, I got back a P0174 code, which is "system too lean bank 2". After checking potential causes, it seems that it could be:

PCV Tube's rubber elbow causing vacuum leak
Intake manifold gaskets that are leaking vacuum
fuel pump going bad
bad Mass Air Flow sensor
bad O2 sensor


Could any of these cause the lurching and then cause the P0174 code to be thrown? I'm not the most mechanically inclined, and would rather narrow down what may be malfunctioning before I tear it all apart (haha).

Also, its a 2005 5.4L FX4

It could also be the FPDM that is located above the spare tire.
Drop the spare tire and take a look to see if the FPDM has any sign of corrosion on the aluminum body. Remove the 2 bolts and look at the back side also.
Many of these are corroded to the extent that the aluminum body allows moisture inside and wreaks havoc with the fuel pressure.
Replacement can be had from Amazon for about $56. Don't worry about the Dorman name. It is fine for the FPDM

Pulled down the spare and checked it out, it looks to be in pretty good condition, also poked around on google and it looks like it'd throw the code P1233 if that was the case.

Just cleaned the mass air flow sensor and cleared codes, will update if problem continues / as I try more solutions.

Truck was running fine on the way home. Second day it began lurching again, then this morning the check engine light came back on. Replacing fuel filter and spark plugs today - also going to try doing a smoke test if time permits.

FWIW, I think a Dorman FPDM is only like $30 on Amazon, if you've got the spare coin...

Okay... a little more than I thought.

The problem has gotten worse since I posted this - ended up experiencing random lacks of acceleration, AC working terribly, and small amounts of knocking have began occurring. After taking it in to have diagnostics run, they first told me the coil on Cylinder 3 is bad (I replaced it the day prior). After telling them this, they decided to pressure test all of the cylinders; all of them were around 4% leakage. I was then told that they believed it was an injector that was bad, and they'd look into that. Towards the end of the day I called once again to see what the verdict was, and they said they were taking it out for a test drive to see if they could get the check engine light to come back on. After their test drive, I was told they were 99% sure it is my cam.

Due to my lack of tools and knowledge to disassemble the engine, and the fact that its a piece of crap with 162,xxx miles anyways, I'm currently looking into a reman engine. Pricing for a Jasper with labor at this shop was $8,077.92. Ended up calling the Ford dealership and they said they have a re-manufactured engine across the state and they could do it for about $6321 + fees - this includes labor as well.

I figure getting a reman engine will restore my truck to a "like-new" enough condition, whereas I won't have to worry about much else besides exhaust, transmission, and suspension issues. Probably my best route when it comes to a truck that I still owe the bank for.