I am creating this thread to detail my experience with codes P0171 and P0174 on my 2003 with a 3.0 V6 non-flex and 182,000 miles. Shortly before Thanksgiving on my way home from work I noticed my check engine light was on. I was sitting at a stop light, so I observed the engine. It didn't seem to run any different, and since I was close enough to the house, I drove it back home. When I hooked my scanner up to the truck, I found codes P0171 and P0174. I have a quality scanner, so I was able to monitor my fuel trims while I test drove the truck around the block. My Short Term Fuel Trims and Long Term Fuel Trims were peaking around +25, so the truck was definitely running lean.

Since I had both codes, I knew that whatever issue I had affected both banks of the engine, so I started looking into vacuum leaks. I had a few hoses that were cracking, so I replaced them, but with no change. Per RonD's repeated advice throughout the forum, I unplugged the Idle Air Control valve while the truck was running, and the idle dropped to around 500 rpms, which meant that were no vacuum leaks. At this point I started thinking about whether I had any other peculiar symptoms, and I remembered that my truck had recently started firing off slower than usual. It also started to hiccup at higher rpms, as if it was momentarily starving for fuel. Because of these two symptoms, I decided to check the fuel pressure with a manual gauge. My fuel pressure was sitting at 50 psi, while Ford's spec for this engine was 60-65 PSI.

At this point I determined that either my fuel pump was weak, or in some way was damaged and unable to maintain proper pressure. I picked up a new fuel pump, and dropped the fuel tank. Upon disassembly the only thing I found wrong was that the hose on top of the fuel pump was severely deteriorated (they all are by now), but I am unsure of the function of this hose, and since I was this far along, I went ahead and replaced the entire fuel pump assembly for peace of mind, re-installed the tank, and changed out the fuel filter on the frame rail. I hooked up my scanner to the truck and set it up so I could watch my fuel trims as I drove the truck. Upon the first test drive I noticed that the Short Term Fuel Trims were back around Zero and were no longer maxing out into the double digits. Over the last few days the Long Term Fuel Trims have also dropped to single digits. I haven't seen the check engine light either, so she's ready to go.

I don't intend for this to be a discussion thread, but I hope this info will help at least a few people out.

 

Good testing

I wouldn't think 50psi fuel pressure would cause that lean condition, but maybe the pump's flow was marginal so when demand went up(driving) fuel pressure drop under 30psi

 

I didn't either, and snapping the throttle to 3k wasn't enough to make a change on the gauge. But my fuel trims at and right off of idle weren't bad, so I knew this was an issue under load. Unfortunately I wasn't able to monitor the fuel pressure while driving, but I can only assume there was an occasional significant drop while driving above 3500 rpms as that is where the fuel trims seemed to skyrocket, and where I would occasionally notice a momentary hiccup.

 

Thanks for the detail write up there buddy. At least both of your rangers have new fuel pumps now

 

how hard is it to change the pump on these? Mine is a rust bucket, i live in illinois lol. So bolts and **** will break

 

On my 2002, I pulled the bed back (bumper came off first) and it was pretty simple. On my 2003 I dropped the tank, but there wasn't much room to get at the connectors on top of the fuel pump, and you run the risk of kinking the lines if you drop the tank too far down without disconnecting the lines first. I had to lower the tank a few inches and then climb over the rear axle to reach the connectors. But my truck is lifted so that won't work on something stock height. People say moving the bed is the easiest on these trucks, and I would have to agree based off of my personal experience.

Now let's hope I never have to do it again.

 

i never have removed the bed lol. Sounds like a bad time lmao

 

If I had to do it again, I would probably put the axle on jackstands and remove the rear wheels. Getting the bed over the tires on my 2002 wasn't fun. Luckily it's a rust free truck so the bolts came out easy. On a rusty truck I would soak the bolts top and bottom at least overnight.

 

Ive always removed the bed i can have the pump out of the truck in less than 30 mins and have never took bumper off i always set the front of bed on tire and rear of bed on the bumper ive tried droppimg the tank twice years ago and broke bolts and or straps i said never again