Truck:
1999 F150 5.4L 4x4 XLT
271k miles
Fuel Sending unit replaced two years ago
EGR issues 1.5 years ago-turned out to be compromised hoses
Two cylinders have blown spark plugs in the last ten years, both repaired with Heli-Coil
Have cleaned the MAF sensor in the past, will probably do that again after posting.

Problem:
Truck idles rough, low and dies. Seems to do fine when gas is applied to ~1.5-2k rpm.

Codes:
P0171 - Lean Bank 1
P0174 - Lean Bank 2
P1131 - Manufacturer Control (Appears to also indicate lean from my research)
P1151 - Manufacturer Control (Appears to also indicate lean from my research)

The first thing I'm going to do is go looking for air leaks, recheck vacuum hoses, etc.

Any help would be appreciated. I'm trying to get the truck fixed to sell it, so I can put the money in the '79 Bronco I picked up last month.

Thanks in advance!

 

The 171/174 codes tells it all.
You have a vacuum leak in the intake system.
This is extra air is detected by the Ox sensors both banks.
This causes the long term fuel trims to shift 'rich'.
This causes the drivability issue you have.
Good luck.

 

So I found the issue (at least its AN issue, but I'm about 90% sure it's THE issue.)

Coming off of the PCV valve, the long rigid piece (Piece E here) that appears to run to the back of the throttle body is just floating around and not connected to anything. I think I've found where it goes, but I've run out of time for the day and will have to pick it back up tomorrow.

It seems like what I've found is actually recessed in the throttle body, but the pictures at the above link make me question that. Hopefully I'll be able to fix this without removing the throttle body, as that's not something I've done before, and as previously mentioned, I just want to fix and sell the truck.

Anyway, I'll continue to document this to hopefully help others out with the issue. Pics to come later, I just don't have time to upload right now.

 

The rubber ELL in the rear of the manifold goes soft from the fumes drawn through the PCV..
The important thing is to understand why the fault affects the system the way it does, as explained.
This is one way the system keeps a check on the 'closed' crankcase system.
Even an unseated dip stick can cause a code.
You found the problem ok.
Good luck.

 

Standard infamous PCV elbow failure.

There are only two types of Triton engines: Those that have already suffered this failure and those that haven't had it happen yet.

Extraordinarily common, no need to expend effort documenting this yet again.

 

If it's common, I won't bother with the pictures. Where can I read more about it? I'm trying to replace it without pulling off the throttle body, and it seems pretty difficult to get to.

 

Here are 464 threads with the phrase "pcv elbow" in each of them: Ford Truck Enthusiasts Forums - Search Results Many of them will directly relate to your issue.

If you cannot get to it with your left hand, you may need to remove the IAC valve to give yourself better access.