2003 Explorer Sport Too Lean

I have a 2003 Explorer Sport 4.0l V-6 with trouble codes P0171 Too Lean Bank 1 and P0174 Too Lean Bank 2. Was told by O'Reilly's that the O2 sensors were bad. Wasted $125 because that wasn't the problem. Still have the light. Engine runs good but now almost stalls when stopped since I put in the new sensors. Any ideas or fixes would be appreciated. Thanks

Welcome to the forum! Too bad you spent the money on O2 sensors before posting here.

Codes P0171 and P0174 would not indicate faulty O2 sensors, but rather that the O2 sensors are doing their job and reporting a lean condition.

Since you have codes for both banks of cylinders, you're looking for something that will effect both banks such as a restricted fuel filter, weak fuel pump (or other condition that could cause low fuel pressure), a vacuum leak, a dirty Mass Air Flow sensor, disconnected intake air hose, intake manifold gasket leak, etc.

You don't happen to have a reuseable oiled air filter do you? If so, start by carefully cleaning the Mass Air Flow (MAF) Sensor with the appropriate cleaner. Heck, even if you don't have a K&N-style filter, try cleaning the MAF.

While you're at the auto parts store getting the MAF sensor cleaner, pick up a bottle of fuel injector cleaner and add it to the fuel in the tank. See if the store has fuel pressure guages available for loan. That may be your next step if cleaning the MAF and injector cleaner has no effect.

Does the engine seem to idle fine and run smooth under load?

-Rod

Thanks for the info Shorod. I did have a K&N filter that I took out last week. I saw this somewhere else today and I did clean the MAF. Didn't appear to help as the light came back on again after I drove it tonight after it dried. I will try the fuel filter and injector cleaner though. Also, I did have a disconnected hose right after the MAF a while ago that caused the light but I didn't read the code because I saw that it was off. I'll also try the pressure gauges afterwards.
It does basically idle well and seems to have good power. I have been getting better gas mileage, but I thought it was the type of gas I've been buying since I moved up here (QT gas). I did just move from FL to MO and that's when I got the light was right after I moved up here. As far as idle, right after I put the new sensors in and was going back to O'Reillys to reset the codes, it was jerky and idle speed dropped to about 350-400 rpm at a stop. Seemed to be ok later tonight when I took it out.
Thanks again.