Btruck

I have a 2001 f150 5.4L that began missing. I checked the codes and am getting P0171 and P0174, banks 1 & 2 running lean.

With the truck idling at operating temperature my live data readings are:

Short term fuel trim 1 from -3.0 to 3
Short term fuel trim 2 from -4.7 to 4.7

Long term fuel trim 1 from -3.1 to 1.6
Long term fuel trim 2 from -3.9 to -1.6

O2 sensor S11 from 0.06 to 0.8
O2 sensor S12 0.75

O2 sensor S21 from 0.05 to 0.8
O2 sensor S22 0.6

Mass air flow sensor 0.9

Everything I've been able to find says that my long term fuel trim should be reading 20% or more.

Does anyone have any idea why I would be running lean but my long term fuel trims are so low?

Seems to me this should be telling me something but I'm not sure what.

Any thoughts or suggestions appreciated.

fishbones182

could be many things. Id start by checking for vacuum leaks and see what you find. I had a truck once that was lean on 1 and 2 and found two vacuum leaks. Fixed them the problem went away was it luck who knows but it fixed it.