P0171 P0174 lean codes
Junior Member
Joined: Nov 2007
Posts: 1
Likes: 0
From: Seattle, WA
It isn't always the MAF or Intake manifold leak
I have a 1998 Ford F150 8' standard-cab, with V-6 4.0L engine, 120K miles on truck.
Reset codes, and at idle everything fine, same for city street driving.
I would get the P0171 & P0174 codes only after the truck was run on the free for 15 min. or longer, and took an exit and came to stop.
No Intake manifold leaks, checked MAF and it checked out, replaced PVC valve, still no change in problem.
So, I replaced fuel filter, and ran tank of clean gas with injector cleaner, still had problem. On advice of my brother, checked fuel system pressure was on the low side of normal range, but replaced fuel pump anyway.
I'm happy to say, problem fixed. According to my brother, around 100K or so miles the fuel pump starts wearing out.
Just a thought for others.
Reset codes, and at idle everything fine, same for city street driving.
I would get the P0171 & P0174 codes only after the truck was run on the free for 15 min. or longer, and took an exit and came to stop.
No Intake manifold leaks, checked MAF and it checked out, replaced PVC valve, still no change in problem.
So, I replaced fuel filter, and ran tank of clean gas with injector cleaner, still had problem. On advice of my brother, checked fuel system pressure was on the low side of normal range, but replaced fuel pump anyway.
I'm happy to say, problem fixed. According to my brother, around 100K or so miles the fuel pump starts wearing out.
Just a thought for others.