JSpitler

I have a 2001 Ford F150 5.4l 4x4 with engine codes P0171 and P0174. I have done so much searching on the internet to try and fix the codes but they keep popping up. I have replaced the pcv valve, cleaned the trottle body and the throttle body spacer i have on it. As well as the mass air flow sensor and the idle air control valve have been cleaned. I havent found a vaccum leak anywhere and i have checked when the engine is cold with carb cleaner to see if their is a change in rpm. Will someone please help me i really dont want to take my truck to a shop for the issues im on a budget and dont want to get screwed over with shop fees for something that i can do for much less.

Marc D

Assuming you have looked at the O2 sensors (unlikely) you'll need to replace all the intake manifold gaskets. Did mine last year. Use Ford parts. Total was about $400 and 12 hours of actual work.