Infamous P0171 & P0174 Codes !?!?

[Hoytman]

Have a 2001 F-150 with a 4.2 V-6 and I'm getting the P0171 & P0174 lean codes. I see several post on this topic that lead in different directions. My truck has 106,500 miles and has been maintained well with no running problems. I see no obvious vacuum leaks but the PCV fits loosely in the valve cover grommet. Are these intakes known for leaking or am I looking at some tired O2 sensors. After clearing codes & driving they will return in a couple of days of course. Should my first move be to clean MAF & replace both front O2 sensors? Truck seems to run well but state inspection laws don't like CEL of course. Any advice appreciated !!

[transgta]

My supercrew had this problem my two vac lines going to the stainless lines off the exhaust manifold had broke down and the rope inside was blocking air. Also heard a lot about dpfe sensor probs. Finally i put a new egr on it all my codes went away. Dont know if this helps but check those two lines i couldnt tell from outside visual had to take off.

[Rpg0]

I would clean the MAF sensor first then clear all codes and try it again.

Just had a friend with the same codes on his 5.4, to which he replaced both O2 sensors, and still had the problem after clearing all codes. Cleaned the MAF sensor and fixed all of his problems.

[Hoytman]

Thanks for the response to my post. FYI -- This 4.2 with 106,000 miles is sucking air @ the intake gasket on both sides therefore it is lean on both banks obviously. Dig deep & yank the intake for gasket replacement.
Sometimes I question all this plastic garbage & low-torque bolts. Of course o-rings will go flat with age & heat -- Just thought I'd follow up. I wish it were the O2's or dirty MAF(that would be much eaiser). Again thanks to AF