2002 Ford F-150

Engine Performance problem
2002 Ford F150 6 cyl Two Wheel Drive Manual 97000 miles

I am a long time certified auto tech and I'm at a dead end.
I have had this same problem for the past year or year and a half. My truck is throwing codes for O2 sensors being too lean. It isn't making sense. I have replaced the upper plenum, MAF twice, DPFE three times, EGR, and both pre-cat O2 sensors twice.
I have checked for vaccuum leaks and post-MAF air leaks. Found nothing.
I am still getting the same symptoms of racing at startup and surging (RPM up and down) at stop lights/signs (mostly when it's cold.
What might the next step be other than taking the truck through the dealership window?
October 24, 2009.

When replaced intake gasket did you reuse the port gaskets and isolator bolt assemblies?
The new isolator bolt assemblies use a green rubber if you used the black color its no good and have to be replaced
and while you have it out check EGR tube and port they do get plugged
you can use carb cleaner or similar solvent and small screw driver to clean it

Oct 24, 2009.
I did use the new port gaskets and isolator bolt assemblies. I'll double check the EGR tube and port, and one other thing I've noticed is that the PCV can get sticky or plugged.I'll give that a shot too.


Oct 25, 2009.
Well, I've checked the EGR ports and tube, was cean.I made sure they were clean when I replaced the EGR valve. But I double checked anyway. The PCV wasn't in the least bit dirty or plugged.
It's still acting up and I'm still at a loss.
One person (wont mention where this person was), suggested flashing the computer. That would be a last resort so I would prefer to try other possible solutions if possible.

Oct 26, 2009.
We always let flashing the PCM as a last
I dont recall having much of an issue with an EGR or acting up
we had a lot of intake gasket failure causing running rough and check engine light on with misfiring codes
Sorry I will try and locate up more for you
just can you get me the codes on it

Oct 26, 2009.
I will get those for you. I'm currently at work and will sleep tomorrow during the day, so I won't have a chance to get those codes for a day or 2.

Oct 26, 2009.
The codes for the first 5 or 6 times were: P0171 System Too Lean - Bank No. 1.
P0174 System Too Lean - Bank No. 2.

The codes for this last time are: P1137 Lack of Downstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1.
P1157 Lack of Downstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2.

Oct 31, 2009.