System Too Lean (Bank 1 & 2)

[Alyusha]

Hey everyone,

1999 Expedition XLT 5.4 4WD

CEL came on tonight and upon checking it came up with P0171 and P0174 which are System Too Lean Bank 1 and System Too Lean Bank 2. I have done some looking around and have come up with several things that could be affecting this.

I am hoping that it is the PCV line because it seems to be an easy and cheapish fix. But like I said, there seems to be at least 4 different things that could be causing this, and I don't know another way to figure it out without replacing each and every part in hopes that it is the part that is causing the codes, and I can't do this.

I seen on another forum that if one code popped up, it could be the O2 sensor, but its unlikely for both to fail at the same time.

So anyways, I am looking for any advice on where to start, or someone who has had the same issues going on and can point me where to look.

Some recent issues that have started, that may or may not be related, but I feel I should disclose...

1. My blower does not seem to blow from the panel vents, its almost as if my heating system is stuck on defrost. When I turn the panel blower on, it blows out on top by the windshield. The vents for the feet work, and the rear works fine.

2. I have noticed that I am not getting as good of gas mileage as I recently did.

3. My gas gauge needle will jump around sometimes. Not from saying 1/4 tank to full tank, but like bobble up and down quickly.. This does not happen all the time, but it defiantly never used to happen!


Thanks for any help.

 

[1955moose]

This a very common problem on all expeditions, especially first and second generation ones. The usual culprits are spark plug/ coil problems. If you read some of the other recent threads, you will see similar problems, and repair solutions. Basicly it's tune up time first, then further diagnosis after that. Please read other owners recommendations, that have done this repair. As far as your heating issue, their are also 2 recent heating issues similar to yours. Again read what they did, it should help you in you diagnosis. Good luck, please post your progress, it helps others like yourself, with future problems.


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[glen r]

I had the same codes a few years ago on my 01. Replaced PCV and all vacuum lines with no affect. Had it smoke tested twice. Second time they found a cracked manifold, apparently cracked when the temp sensor was replaced.

 

[Bedrck47]

I once read that anytime a code comes up that refers to many items and O2 sensors are involved Would be best to check all item and save the O2 sensors for last as many things can cause false O2 readings

Item #1 Vacuum lines could be the problem.

Item #2 could be a need for a tune up Plugs and new boots

Item #3 Possible a bad float sensor I had that on my 01 The pump was good but the float was the cause of false readings

The tank level is a variable resistor and the action of the float changes the readings Sometimes over years of fill ups and low fuel levels the variable resistors get worn and gives false readings

 

[docraymund]

Try taking fuel pressure readings might be a weak fuel pump. Replace the fuel filter. Clean the MAF sensor.

 

[Alyusha]

Thanks for all the info everyone. I did check the PCV elbow and it looks perfect.

I think I am going to try cleaning the MAF sensor first and see what happens. Is this pretty accurate info as far as the 5.4 engines go?

Part 1 -How to Clean the Ford MAF Sensor (Ford 4.2L, 4.6L, 5.4L)

Thanks.

 

[Bedrck47]

read this also

http://www.expeditionforum.com/191356-post1.html

 

[Alyusha]

Maybe I should have said this in the first place, but my alternator did just die and I had a garage replace it the day before CEL came on. Is there anything in in the process of replacing the alternator that may have been unplugged or removed that may be related to this?

 

[Bedrck47]

Shouldn't be anything that needed to be unplugged to change out the alternator. But then its hard to tell what or how other people do things

 

[glen r]

They would have been working around the front of the intake.

 

[1955moose]

We'll here's a dumb question, if the problem started after the alternator install, why are you messing with it? Bring it back to them. We collectively can help you figure out problem, but why? Let them fix it. It could be coinsidence, but make them take the first step. These are not easy SUVs to wrench on. If you had a shop do an easy install like an alternator, your not going to like digging into tune-up related items.


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[shadow460]

This^^^. They may have ripped or disconnected a vacuum line when they were replacing the alternator.

For those codes, thoroughly check your vacuum lines first. Forget the O2 sensors--those are just money makers for the parts store. They do need replaced once in a while, but not for PO171 and 174.
I've heard of the ladder gasket (between upper and lower intake manifolds) leaking and causing them. You could have a bad gasket on anything that's attached to the throttle body... EGR valve, Idle Air Control, TB to elbow, elbow to intake, , plenum to throttle body, air cleaner to plenum, etc. Also check the brake booster hose and both the PCV supply (from the valve itself) and return.
It may seem like a lot to check but you can knock it all out in just a few minutes by feel or sight, or, if that doesn't work, with carb cleaner.
If it's a hose, head to the junkyard for a replacement. If it's a gasket, the parts store can fix you up.

 

[Solefly87]

Hey everyone,

1999 Expedition XLT 5.4 4WD

CEL came on tonight and upon checking it came up with P0171 and P0174 which are System Too Lean Bank 1 and System Too Lean Bank 2. I have done some looking around and have come up with several things that could be affecting this.

I am hoping that it is the PCV line because it seems to be an easy and cheapish fix. But like I said, there seems to be at least 4 different things that could be causing this, and I don't know another way to figure it out without replacing each and every part in hopes that it is the part that is causing the codes, and I can't do this.

I seen on another forum that if one code popped up, it could be the O2 sensor, but its unlikely for both to fail at the same time.

So anyways, I am looking for any advice on where to start, or someone who has had the same issues going on and can point me where to look.

Some recent issues that have started, that may or may not be related, but I feel I should disclose...

1. My blower does not seem to blow from the panel vents, its almost as if my heating system is stuck on defrost. When I turn the panel blower on, it blows out on top by the windshield. The vents for the feet work, and the rear works fine.

2. I have noticed that I am not getting as good of gas mileage as I recently did.

3. My gas gauge needle will jump around sometimes. Not from saying 1/4 tank to full tank, but like bobble up and down quickly.. This does not happen all the time, but it defiantly never used to happen!


Thanks for any help.

Can't really chime in on CEL codes but I had the same problem with my a/c only blowing thru defrost. It's called default defrost mode. From what I've read it's what happens when you have a vacuum leak. This video here helped fix my problem for $2. Hope this helps scratch one problem away.

http://youtu.be/gtVohg8qIEA

 

[Alyusha]

Thanks again for all the info.

I have considered taking it back to the garage, but I do not think they will do anything without charging me. I almost guarantee they will take blame for the issue and just fix it. They replaced my steering gear once, and I understand this will call for an alignment afterwards, but they completely screwed up how my steering wheel was attached to it, and now when driving straight, my steering wheel is at a 90 degree angle like I am turning. This alone seems like a pretty simple thing to prevent, or at least make sure you get it straight.

Anyways, I have concluded that this has to be a vacuum leak somewhere, it has just been a pain to find where it is. The weather here has been 0 to -5 and I have no garage, so I have just been dealing with the wasted gas, running my defrost for heat.

I have never been a fan of taking any car to a garage for anything more than tires (which I never had the proper equipment to change anyways) just because I felt like they would purposely do something else to the vehicle, just so you come back and spend more $$$. But then I got this truck, and everything that breaks happens on the coldest days of winter and are located in places I do not feel like getting to. So I sucked it up and took it to a garage, and it seems like every time I do, something else goes wrong right after.

I am gonna give it one last shot to look for a leak before I call them and see if they can at least inspect it for free. At least today is int he 40's.

Thanks again everyone, I am still reading for any new ideas, and will post the results once I get them!

 

[fryguy]

I have considered taking it back to the garage, but I do not think they will do anything without charging me. I almost guarantee they will take blame for the issue and just fix it. They replaced my steering gear once, and I understand this will call for an alignment afterwards, but they completely screwed up how my steering wheel was attached to it, and now when driving straight, my steering wheel is at a 90 degree angle like I am turning. This alone seems like a pretty simple thing to prevent, or at least make sure you get it straight.

Sounds like you need to find a new mechanic.


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[1955moose]

Yeah we can all get together and start a expedition/ f150 garage. The smart shops do specialize. Think of all the happy customers we'd have.


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[Monkey Tales]

have you had a chance to do he carb cleaner test to find a vacuum leak?

 

[dschallmo98expo]

I had the same issue as well. However check the snorkel where it bolts to the throttle body, Make sure that the underside of the grommet is not folded back on its self. This will cause the MAS to give a false reading and give those codes. Being that the replaced the altenator, more than likely the took of the snorkel. and since you have the snorkel off clean the MAS.

 

[dschallmo98expo]

as far as fuel gauge, replace filter and then look at fuel pump. Could be float issue.

 

[Alyusha]

Ended up being a rubber elbow vacuum hose near center of the firewall. Amazing how something so small can cause such issues.

BTW, I kept checking my CEL to make sure nothing new popped up, and after a few days, a new one did show up. P0401 - EGR.

After replacing this hose with a $1 replacement, cleared the codes and it runs perfect now. Cleaned out the system too, I am sure that hose sucking up all that dirty road salt was not great.