My son's truck recently had service engine light, I read the code with my cheap little NAPA reader and got a P0171. Did some searching and looks like maybe a vacuum leak. We are not mechanics but can turn a few wrenches. Wondering has anyone experienced this code with the 5.4L motor and what did they find

He did recently put fuel in and today it was upper cold out 2 deg above zero - not sure if that has a factor for this code

any help is appreciated

 

A P0171 is a lean condition on bank 1 (passenger side) It could be 1 of several things.
EGR valve or a bad DPFE
Low fuel volume delivery
Vacuum leak
Dirty MAF sensor. I think TSB 98-23-10 might address that
www.aa1car.com/library/ford_lean_codes.htm

 

It's more likely a vacuum leak

 

Thanks for the replies, I deleted the code. The service engine light has not come back on

going to keep an eye on it

 

x2, probably a vacuum leak and not unique to the 5.4l.
It could take a little while to come back if a hose is just starting to fail.
Look for a soft spot in a vacuum hose, usually near an engine connection where there is more heat.
Most likely fails are the PCV hose near the throttle body connection or a cracked plastic vacuum hose fitting tee or elbow.