I have tried to search for my issues but haven't found much. Here goes...

I have an 01 F-150 5.4 4X4. Everything was fine until I put a K&N air filter in the stock box and took the small tube that goes into the fender off. At first the engine surged and then leveled out. Normal, then about three engine starts later the check engine light comes on. I wait a while and then disconnect the battery figureing that it would reset. Well, same problem, once again. Take it up to Autozone, pull the codes and it comes up with (If I remember right) PO-170 and PO171. Banks lean. What gives? I don't think it would be the O2;s cause I only have 43K for mileage...

The other problem I have is with the wifes 97 Expedition EB 5.4 4X4. It has 183K on it. The check engine light comes on and code reads bank one lean (I think po-170) I figure it's and O2. I replace the driver's side front O2. At first all is well. Three days later check engine light comes on again. It reads PO-171. I replace the passenger side O2. Thinking I am done with issues, The light kicks on again telling me bank one is lean.. Now what?

Well thanks for reading and for any help someone could give.

 

Look for vacuum leaks. They are common causes of lean conditions

 

On your 150, did you oil the filter? If yes did you over oil it and get the air meter coated with oil?
Clean the air meter with special cleaner made for the use and put a stock filter back in.

In the EXP, there could be an air leak betrween the air meter and the throttle body as well as a hose has gone bad admittiing unmetered air.

You may not see the effects of any repairs for two or more drive cycles on both trucks.

 

Thanks for the response guys. Vac, leak, hmmm it could be. In all my haste that is one thing I didn't check.

As far as the oil, I was pretty carefull to not over do it. I will however check it later.

Whats the deal with putting a stock air filter in it? Is it just to see if the check engine light will stay off or is there a problem with my 01 F-150's computer learning new stuff? I wouldn't think there would be a problem with all the aftermarket CAI kits for it.

One guy at the parts counter said it was probably an injector that was clogged and wanted me to buy a $30 cleaner for it. What is good as an addative that I could put in the tank to clean the injectors...something that works? Seafoam maybe?

Thanks again..

 

Seafoam is one of the best products out there... I hope its not $30, though, it would be worth it.

 

You need to spray the filiments in the MAF with brake parts cleaner or electrical contact cleaner. They probably got a little oil residue on them causing it to run a little lean.
As for the EXPY, check the PCV hose elbows (espeially the rear one where it connects to the intake manifold), they are know to crack and cause a vacuum leak.

Oh and welcome t0 the forum. Enjoy the boards

 

I have the exact thing going on right now in my 1999 F-250 with a V-10. Same codes, check engine light, and a crappy idle. I replaced the fuel filter. No difference. I checked the fuel pressure at the rail and it was 32psi at idle. I have my stock intake and filter, problems started after I put an aftermarket cat-back system on it. Any suggestions?
And yes I realize I'm in the wrong area but I find it too strange that we have completely different hardware with the exact same problem.

 

Check your PCV hose elbows as well. Sounds like a vacuum leak.

 

Well, I sprayed the MAF sensor, checked for leaks on the F150 and cleared the code. I have started it three times but haven't driven it yet. Hope all is well with this one.

Now for the Expedition, I sprayed the MAF, checked connections and replaced a questionable hose on the back of the intake. Its the one that loops around to the PCV. It may have been okay but anyway...I also bought some seafoam and poured some through the hose on the back of the intake. Then I poured the rest into the gas tank. I am on my way out to get the check engine light extinguished (Auto Zone) Hopefully it will stay out for a while this time. I will let you know how it goes...

Nzirbel.. hope you get yours figured out. mine didn't rough idle after initial start up. Neither one did...Good luck

 

I got mine fixed last night and no check engine light on yet. I changed the fuel filter-no help but at 90,000 miles it needed it. I also checked all the pcv lines, had a crack in one. Replaced that, cleaned the MAF sensor, reset the PCM and life is good. Glad you guys could help, saved me throwing a few hundred bucks at parts I didn't need! Fixed and running great for less than $30!

 

Glad to help

 

AArrggg, well the light came on again in the F-150. I swapped the stock air filter back in, re-installed the end piece that connects the air box to the fender and disconnected the battery. It stumbled initially but then cleared up. I drove it for about 20 minutes and no light...yeah, we will see. I am sure tomorrow it will light up again.

I haven't driven the Expedition yet.

 

When it comes back on, get the code read again and post it here.

 

PO 170 (bank one lean)
PO 174 (bank two lean) these are the two codes that just came up again. After only maybe 25 miles of driving. I haven't driven the EXPY yet but I am sure it will be the same.

 

Note: everything was fine until I put the air filter in!!!!!!!
The lean codes are telling you you have 'unaccounted for' air leaks.
Is there a hose off or miss aligned between the air meter and the throttle body; the only place affected by your work!