2010 Ford Escape 2.5 - P0171 Too Lean

[dogememe]

Only thing I did today was change the oil and filter and change the nasty air filter.

Tomorrow I'm going to see if any crud ended up in the MAF sensor from when I changed the air filter.

If it's not a MAF issue I'd say the only other things are fuel delivery issue, o2 sensor, or vacuum leak right?

It drives ok but it seems a bit unhappy. Earlier I was trying to merge into a busy road from my apartment and the Escape hesitating badly for several seconds was not safe. But it didn't set the code until hours later while it seems to be driving ok.

 

[michaelluscher]

 

[dogememe]

Thanks for the tip on the purge valve I will check that it is right next to the throttle body and easy to get to.

 

[oil_film_movies]

Too lean, to me I'd first check the fuel injector performance. If one or more have gunk on them, not enough fuel gets sprayed.
One web reference did point a lot to fuel system issues:

What are the causes of the P0171 code?
Causes of the P0171 code may include:

A faulty fuel pressure regulator
A weak fuel pump
A clogged fuel filter
A faulty powertrain control module
A vacuum leak
Faulty injector(s)
Faulty oxygen sensor(s)
A faulty mass air flow sensor

 

[SubieRubyRoo]

Yeah I did the same thing and had the same results on my Fusion... oil change and air filter change, then CEL and run like crap... I don't remember what code it was, but I had ended up kinking the harness right at the connector, and it broke continuity. I had to buy the WPT1241 harness off Amazon, and cut my MAF harness back about 2" and then solder and heatshrink them. As soon as I finished that and fired it back up, everything was fine and has been.

 

[Trav]

Look at the fuel trims first, then check for vacuum or air intake leaks, check your air filter housing, make sure its tight and any hoses or tubes are tight and not cracked, don't throw parts at it.

 

[dogememe]

LTFT was +29% cleaned the dead bug out of the MAF. Everything looks ok otherwise. I replaced that Evap purge thing because I felt the slightest trace of vacuum coming from it. How long does it take for the LTFT to relearn? After running the car for a bit it went to 22%. But it didn't go further towards 0.

 

[dogememe]

Nope, it drives better but LTFT is still hanging out between 21 and 29% I will spray water to check for a vacuum leak next.

 

[Falcon_LS]

Take a good look at your exhaust system and make sure there are no leaks.

Had a similar issue on a Ford Edge that I worked on a while back, and the owner literally threw money at it to fix it - new MAF, new injectors, new oxygen sensors and new fuel pump. The one thing he didn't address was an exhaust leak, thinking it was the exhaust manifold. It turned out to be an upstream oxygen sensor bung, which was rusty and snapped off.

 

[Whimsey]

Originally Posted by Falcon_LS
Take a good look at your exhaust system and make sure there are no leaks.

Had a similar issue on a Ford Edge that I worked on a while back, and the owner literally threw money at it to fix it - new MAF, new injectors, new oxygen sensors and new fuel pump. The one thing he didn't address was an exhaust leak, thinking it was the exhaust manifold. It turned out to be an upstream oxygen sensor bung, which was rusty and snapped off.


I had a rotted driver's side cat that was leaking and threw a P0171 code on my 2002 F-150 4.6. I believe with Ford once the LTFT gets above +25% for a certain amount of cycles it'll trigger the P0171.

Whimsey

 

[dogememe]

Comparing STFT at idle and 2500rpm showed there was no vacuum leak. It just got more lean at higher RPMs. I took a gamble and installed a new MAF sensor. Immediately upon startup the STFT went negative to counteract LTFT. I guess the original MAF got damaged by the dead bug so even after cleaning something was still wrong. Glad this was an easy one! Thanks all for your help!