bought this 2001 f 150 4.6l from my dad with 70.000 miles. very well taken care of! like every man i coldn't resist adding stuff!! installed k&n filter and throttle airaid throttle body spacer.a couple of weeks later onemorning started truck to warm up and when i came back theC.E.L was on! checked and got codes : po171 and p0174. can anybody point me the right direction ? thank you.

 

i just looked it up and both codes have to do with the O2 sensors
"PO171-Oxygen sensor not switching - system was at adaptive limits - Single, Right or Rear HO2S - Fuel control"
"PO174-Oxygen sensor was slow in switching Single, Right or Rear HO2S - Fuel control"

This is where i found them...
http://www.troublecodes.net/Ford/

 

If you have both PO171 (bank 1 lean) and PO174 (bank 2 lean) it seems unlikely that both O2 sensors are bad. More likely is that a common element is causing the error codes. Try cleaning the MAF sensor with an approved cleaner and look for a vacuum leak, such as around the PCV valve or the rubber hoses and tubing. It could be a stopped up fuel filter or a bad fuel pump that isn't supplying enough fuel at higher RPMs. Something is making both engine banks too lean.

 

If this started after the installation of the accessories, check to see if there are any vacuum leaks where you did the work. Lots of times with performance modifications you may need to recalibrate the PCM to accomodate the extra air or fuel that is being called for.