1999 F150 4x4 4.2l v6
I just bought the truck two weeks ago, it had P0401, P0171, and P0174 codes. It feels a bit gutless under normal driving conditions: if I drive 15-25mph for any length of time, or Idle at a stoplight, when I start driving again it hesitates until about 2500rpm then it gets it's "git-up" back. Also If I decel down a hill and roll to a stop the Idle will drop to 500RPM and it will miss and try to die. The P07xx are Banks 1&2 too Lean, and the P0401 Is insufficient EGR. I took the EGR off and thoroughly cleaned it and checked that it had no vac at idle from the green vacuum line, Cleaned the Mass Air Sensor with mas cleaning spray, and went nuts with two cans of Carb Cleaner spraying every vacuum line and gasket I could reach (thinking it was a vacuum leak); No Luck.
No EGR code has popped up again, but I'm still getting the banks 1&2 sensor 1 too lean codes. Can't find a vacuum Leak, any Ideas or suggestions?

 

any ideas?

 

Lean codes can be caused by misfires, have you done a tune up and air and fuel filters?

 

i know u said u couldnt find a leak but what u are talking about is what my truck did to me a while back...codes and all...in the end it WAS a vac leak.really the only problem ive had with my truck is darn leaks all the time on the vac lines...not saying ur wrong just giving my two cents