Dreaded P0174. I've checked everything...what could it be?

[RedBolide]

I had posted earlier about lean codes on my '00 Explorer Sport, and fixed it easily by replacing an evap hose. Well, now P0174 (bank 2 lean) is back and I can't figure out why. It appears intermittently and only on this bank. I have done the following:
-I smoke tested again, and there's no vacuum leaks anywhere
-O2 sensors are reading right (upstream sensors fluctuate, downstream sensor remains constant)
-MAF sensor reads 0.01 lb/s at idle and 0.03 lb/s at 2500rpm
-Short term fuel trims look good, usually around 0 +/- 3%
-Long term fuel trim is surprisingly high, sitting around 12-20%
Aside from the high long term fuel trim, I can't see anything that appears out of the ordinary. Idle is smooth, performance is good, but the check engine light keeps popping up. Does anyone have any ideas of what else to check, or why the long term fuel trim is so high even though the short term remains low? Any help is greatly appreciated!

 

[410Fortune]

2000 sport with a SOHC or OHV?
Have you tested fuel pressure?

 

[RedBolide]

2000 sport with a SOHC or OHV?
Have you tested fuel pressure?

It's OHV. I haven't checked fuel pressure though, I can see if I can pick up a gauge to check. That's a good idea.

 

[410Fortune]

po174 means that the computer detects a lean condition, it has attempted to dump more fuel to compensate but it was not enough so it is still "overly lean" on bank 2
This can be caused by low fuel pressure or air entering the intake that is un metered (did not go through the mas, on ohv usually intake plenum O ring gaskets) May not be visible with smoke test until everything is warmed up or possibly under load at WOT

 

[FijiBill]

Strange that it is only on bank2 though if it was a fuel issue. Maybe an exhaust leak is fooling that bank's O2 sensor?

 

[410Fortune]

or one injector is weaker then the others, or the code maybe coming for the other bank just not set yet, or it could be air leaks?
First things first check fuel rail pressure

Computer codes are a GOOD THING to have because we can FIX the truck before it melts to the ground