4 Codes and Poor Idle 2002 4.6L

[ajskyman]

Hi all, I've got a 2002 Explorer 4.6L that has been acting up as of late.
The other day, the car threw four codes (P0171, P0174, P1130, P1131). After a bit of research I replaced the fuel filter (what a joy), cleaned the MAF with CRC MAF cleaner, and added a bottle of Lucas injector cleaner to the fuel. After this process, I cleared the codes and thought all was well, however it didn't last long. The car now idles rough and yet seems to perform fine while driving. Today was the first time that it "stalled" at a stop light. After this, two more codes returned: P0171 and P0174, both being lean conditions for the two O2 banks.
So now I'm at a bit of a loss due to how quickly this issue appeared. My biggest suspect would be the MAF, however I have cleaned it several times before, following directions on the can, and never have had an issue. I am not disregarding the possibility of a vacuum leak, but I wouldn't have expected it to come on so abruptly.

Any advice is much appreciated and I will try to respond to any questions whenever I have a spare moment.

 

[tmds3]

Usually when it throws both 171 and 174 it means the MAF is bad, at least in my experience, pretty easy part to change but kinda pricy around 100 if I remember right

 

[ajskyman]

Usually when it throws both 171 and 174 it means the MAF is bad, at least in my experience, pretty easy part to change but kinda pricy around 100 if I remember right

Thanks for the suggestion!
Ran the car today and it was great, until it came up to operating temperature and immediately started to run poorly. Shut off the car, disconnected the maf and restarted (forcing into safe mode) and it ran like a dream even after letting it run for 10+ minutes. Will install a new one tomorrow and I will report back with the results.

 

[ajskyman]

Problem Fixed

Got the new MAF installed and no dice. Took off the decorative engine cover and sure enough, there was a hole in one of the vacuum line elbows. The issue was the same one detailed by SyberTiger here. Luckily I was able to take the MAF back and receive a refund!
Thanks again!

 

[ponkotsu]

I was throwing parts at my car until I got a scanner. Thought for sure I had bad O2 sensors but the scanner is saying vacuum leak. I'm using Scan XL with an $8 USB connector. Software was cheaper than 2 new O2 sensors. Yours does sound like a vacuum leak. Could be lots of small leaks causing the issue. I think disconnecting the MAF sensor reinforces a vacuum leak theory. The MAF is metering the air into the engine so it can adjust fuel. If you have unmetered air, it will run better without the MAF connected because it's relying only on the O2 sensors to adjust the mixture. Good news is your O2's are probably fine. In my case I've yet to find the stupid vacuum leak but I'm going to try again today.

 

[Number4]

The 4.6l is notorious for throttle body issues. Basically it gums up from oil via the pcv.
There is TSB on this starting with only 10k miles!!!!!

My first question to you, would be have you disconnected the battery right before this happened?

Also, your model has a crappy rubber 90 degree connector hose going to the driverside front on the Throttle body (or egr or something) I believe. These crack though you may not see it. Move it around.

Back to the throttle body. This is your second area to look at after the rubber 90 degree piece (do this one either way.) Both of these items will cost nothing. Other than buying the little rubber piece.
Remove your air intake hose.
Move the butterfly valve on the throttle body with your finger and take a rag and clean the gunk from all around where the valve closes on the throttle body.
Just a cloth rag and friction will make a difference. (there is a special cleaner for the throttle body, but it may require removal of the unit.)
Now, put everything back together and drive happy.

Trust me, try this before throwing any money at it. Read the forums and you'll see how many people have wasted money replacing parts that weren't bad. Including the IAC.