4 liter not sohc....To give a little history, I just returned from a week-end 600 mi round trip. I had a 21 cu.ft. cargo carrier mounted to the roof rack. On the way home I noticed a howling sound that I attributed to wind on the carrier. Did not experience this on the going out of town trip. May have had a tail wind or something. About 90 mi from home, the Check engine light came on. All gauges read normal, so I proceeded home. Traveling with 5 females (not all in same vehicle) meant frequent potty breaks. At rest stops the engine seemed to run and sound normal, but returning to highway speeds might have been a little labored. Hard to tell when you been running 70 for an hour, everyting else seems slow. It did kick out of OD a couple of times on both legs of the trip. Each fill-up, showed worse gas milage. Normally I drive a mile to work and a mile back. the mileage sucks (8 mpg) with such short runs. It got 19.3 first 150, 17.3 next, 15.2 next and I'm guessing about 12 last as I haven't refilled yet. Wind may be part of the problem there. I got blown about a bit.
Upon returning , I had the code pulled and it came up P1131..HO2 lean.
Then the code was erased. Has not yet reappeared. After a long discussion with the parts man at auto Zone, (retired with 30+yrs exp at GM dealers mostly) we decided it might have been due to the drag created by the carrier.
Vehicle has 67xxx mi and 4wd auto.
Does any of this sound logical to you guys or do I need to look into something else.
Carrier is now off the vehicle and I'm back to my daily 1x1 trips.

 

here are the things the book says to check when code P1130 or P1131 are captured that is where I would start
Electrical:
1 Short to VPWR in
harness or HO2S
Water in harness
connector
2 Open/Shorted HO2S
circuit
3 Corrosion or poor
mating terminals
and wiring
4 Damaged HO2S
5 Damaged PCM

Fuel System:
1 Excessive fuel
pressure
2 Leaking
/contaminated
fuel injectors
3 Leaking fuel
pressure
regulator
4 Low fuel pressure
or running out of
fuel
5 Vapor recovery
system

Induction System:
1 Air leaks after
the MAF
2 Vacuum Leaks
3 PCV system
4 Improperly seated
engine oil
dipstick

EGR System:
1 Leaking gasket
2 Stuck EGR valve
3 Leaking diaphragm
or EVR

Base Engine:
1 Oil overfill
2 Cam timing
3 Cylinder
compression
4 Exhaust leaks
before or near
the HO2S(s)

 

I have the exact same Explorer as you. I recently experienced the exact same circumstances as you are including the fuel mileage decrease. I could not diagnose the problem everything checked out normal and I kept driving it. the fuel pump finally gave up. The funny thing was that it would run ok as long as the fuel pump was cool, the more it ran the worse it would run until it would not run anymore. That was why I could not diagnose it in the shop, the pump was cool and performed according to specs. It finally quit 600 miles from home and I ended up changing the fuel pump in an Auto Zone parking lot in the dark on a Saturday night. If the code comes back and progresses to both banks running lean as mine did I would say get a new fuel pump.

 

Well it finally happened again. This time on a road trip of 250 mi one way.(No cargo carrier this time, new air filter). This time it started runing rough for about 5 miles and the check engine light would occassionally flash several times, then be steady and flash again. I've got a few days before the trip home where the tools are. Will have to have the codes pulled then. The codes before did not indicate left bank or right bank. Should they ? What does the flashing light indicate ?