Forgot to mention he had a new fuel pump installed about 2 years ago. One of the shops said they did several fuel system checks with no avail, not sure if they actually checked each injector though.

 

Nice to know others are having this same issue, if he takes it in, I will update, but we are trying to figure it out on our own first.

 

Yours is the first one that I heard of (besides my Navi) that has ONLY Bank 2 lean. All my searches have turned up vehicles that have BOTH Banks 1 & 2 lean (P0171 and P0174).

 

I noticed that as well, I just talked to my uncle and he did say the first shop he went to did replace the PCV valve and all the elbows on the line.

I was thinking that since it is only one side that is lean, it might be a fuel injector problem like mentioned before.

 

My uncle has not gotten back to me yet, but I came across a really nice article about these codes: http://repairpal.com/OBD-Code-P0171-and-P0174

Kind of looks like dirty or faulty injectors or leaking intake manifold if it is not the simple stuff like MAF sensor, PCV system, EGR, or fuel filter.

 

Update: Problem is fixed! Talked to my uncle today and he decided to change the fuel filter. He must have gotten some terrible gas somewhere in Arizona on his way back to Missouri a few months back, because the filter was full of sludge and weighed like 8 times more than the new filter did. After the swap the Navi runs perfect with tons of power.

Two interesting things: You would have figured that both lean codes would have been triggered by the fuel starvation caused by the dirty filter. He supposedly only got the P0174 bank 2 lean from the scanner.

The guys at the original shop must not have wanted anything to do with the Navi since their fuel system check must of only involved putting a pressure gauge on the fuel rail at idle. Further testing under load most likely would have indicated low fuel pressure caused by the filter.

Anyway, he is going to sell me this minty 1999 Lincoln with 128K for $5500. I can't wait to fly down from Wisconsin and pick it up!

 

Hmm, go figure!

 

Hmmmm. I replaced my Navi's fuel filter 9k miles ago. Come to think of it, within 1500 miles after changing out the fuel filter, the P0174 code started poping up.

Exactly. How in the world would that only affect the DS bank?

My Navi will run around 500+ miles before it resets only the P0174 code. Each time it sets the code, the freeze frame data indicates that the vehicle was at ~800 rpm when the code sets, (so it must be a relatively small vacuum leak). If the fuel filter or fuel pump was restricting the fuel flow, not only would I expect to set both the P0171/P0174 codes, I would expect the freeze frame data to indicate that the code/s were being set at higher rpm as opposed to being set at idle.

Anybody try to make a home made smoke machine?

 

just got the same codes on my 98 expy 4.6L, i haven't cheched out anything other than reading the codes and was just wondering if this pcv line problem is a common one with the modular v8's

 

My pcv pipe turned out to be OK, then I started to suspect the plugs. Bingo! New plugs, no worries and much better performance, too! As I understand it, the little rubber elbow is a big problem on the V8s, not sure tho if it applies to the 4.6 or not.

 

I've got a 2000 Expedition 4x4 5.4L with 186K miles. The mileage had been deteriorating for some time now and I had gone through quite a bit of fuel injector cleaner thinking that would help. It didn't. A few weeks ago the service engine soon light came on with accompanying P0171 and P0174 codes. I read several strings on those codes and decided to start by cleaning the MAF sensor. I pulled the MAF sensor (had to buy some tamper proof torx tips) and used CRC MAF sensor cleaner I got at Advance Auto. I reset the light & codes. Light & codes came back in 150 miles. I next changed the PCV valve & vacuum line. Old one had pretty good vacuum, but I decided to change anyway since I had bought it ahead of time ($33 from dealer) in case the old one disintegrated when I pulled it off. PCV valve had 93K miles and was nearly due for replacement anyway. Reset the light & codes, which came back on again in 150 miles. I next bought the rubber grommet that the PCV valve goes into at the valve cover ($3 at dealer). The old one was oil soaked and loose. You can buy that grommet by itself and it comes with the motorcraft PCV valve from the dealer but does not come with the hose/PCV valve combination. Making a short story long, the $3 grommet seems to have taken care of the issue. Light has been out for 350 miles now and mileage is headed back in the right direction. The MAF sensor needed cleaning anyway since I've never cleaned it and have been using K&N filters which have been said to leave oil on the sensor.

 

guys thanks, same problem on my 97 Expy 5.4 98 E-250 5.4 the rear elbow was crushed,burnt, and had a hole in it, can't believe it even idled. bought a new set-up fromthe dealer fixed it right up!! Now seem to have the same problem on 98 E-250 5.4 did replace the rear elbow with a pcv elbow off of a "Dodge", sorry, it fit perfect had it lying around. Lite went out for awile, now on again. Have been reading all the threads about: cleaning MAF, checking grommet, look for any vacuum leak, change air filter, lucas, seafoam spray wd-40 under manifold. Will do all of these and post what worked for me. Hopefully one of these quick fixes will do the trick. Thanks again for all the great posts. Use these for my 99 F350 7.3 C/C dually 4x4 longbed also. SITE IS AWESOME!!!!!!!

 

Well use a nickel leave a nickel . Thanks Guys . I have a 99 expedition 5.4 160 K on it for my wife . She loves it , I do my own easy maintenance Brakes ,2 spark plug coils alternator MAF , rear heater radiator , , an other stuff but the P0174/P0171 very random was not easy until I found you friends. Yep I changed the PVC but never thought of looking at the very back of the line that connects through the Heater junction at the intake. There it was the classic little collapse and hole at the back you cant find without removing. Easy fix cut 3 " of 3/8s gasoline rubber hose I had in the garage to replace the short line and good to go for free. after I reset the ODB system. 10 minutes and o.oo $ . I wish I could post the picture of the line , collapse. If you just feel the elbow and its mushy its done. No need for dealer parts.
Just a thanks for the experience of others maybe Ill post other things I have found

 

Just wanted to keep the love train rollin'. I have chased the "system lean" code on bank 1 for several weeks ('98 Exp 5.4) but knew that if I kept on reading I would find the answer. Read about the boot at the rear of the engine. Squeezed my arm back in there and, while trying to remove it, felt the hole in the 90. $31 for the part and ran all day with no stumbling, stalling, or surging. Free wisdom rocks!

Thanks to all who beat their head on this wall before me.

 

I had the same problem, but before I fixed the problem i erased the codes by mistake, needless to say, i read after about the codes here and went and troubleshot around my lines. I found that elbow in the back and sure enough, eaten by whatever goes through it and I guess the heat and all. I went and got the part at checker auto parts for 4-5$ and replaced it. I did it today, and did not move my vehicle yet because i also replaced the water pump and did the maf cleaning thing too. so it took me a while.(no tools had to borrow from my neighbor) after this i tried driving around the neighbor hood and to the lonely streets out of town, and seems to have more power and no check engine light yet. ABS still there but i just read about the sensor so i will be doing that tomorrow. The reason for mu post is to thank everyone that has given their two cents in this website!!! It really does help out the newbies in mechanical automotive replacing stuff, like my self. Thanks! me expy me expy me I win.