P0171 p0174 codes please help

[Insane451]

I have a 2002 expedition 5.4L XLT and about a week and a half ago I got the p0171 and p0174 codes so I cleaned the MAF and throttle body I looked for vacuum leaks and couldn't find any and the check engine light was reset. We drove my truck over 1500 miles over thanksgiving and the whole time the light stayed off and now it's back. The only symptom I have is excessive fuel consumption, it used a quarter tank to go 60 miles yesterday. No rough idle, which is what I would expect if I had a vacuum leak based on past experience with vacuum leaks, it runs great and idles smooth. The only other condition was the first time the light came on we were in below freezing temps in Iowa and we drove to Oklahoma where it was in the 60's and 70's all week and then when the light came back on last night we were in below freezing temps again in Iowa. I'm going to clean the MAF again today and reset the codes. Any help would be great thank you.

 

[Bedrck47]

The following was copied from the 2002 Ford Service Manual

P0171 - System to Lean (Bank 1)

The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. Refer to Section 1 , Powertrain Control Software, Fuel Trim for more information.

Air Measurement System
MAF sensor (contaminated, damaged, malfunctioning, etc.)
Fuel System
Fuel pressure regulator (leaking, malfunctioning, etc.).
Fuel filter plugged, dirty.
Fuel pump (weak, check valve leaking, etc.).
Leaking/contaminated fuel injectors.
Low fuel pressure or running out of fuel.
EVAP canister purge valve leaking (when canister is "clean").
Fuel supply line restricted.
Fuel rail pressure sensor (incorrect reading).
Air Induction System
Air leaks after the MAF.
Vacuum Leaks.
PCV system (leak, valve stuck open, etc.)
Improperly seated engine oil dipstick.
Exhaust System
Exhaust leaks before or near the HO2Ss (exhaust manifold gasket, mating gaskets, etc.)..
EGR System
EGR valve tube/gasket leak
EVR solenoid vacuum leak
Secondary Air Injection
Damaged/malfunctioning secondary air injection system (mechanically stuck valve).
View Freeze Frame Data to determine operating conditions when DTC was set. Observe LONGFT1 and 2 PID(s). Refer to Section 2 , Adaptive Fuel DTCs Diagnostic Techniques for more information.

P0174 - System to Lean (Bank 2)

The Adaptive Fuel Strategy continuously monitors the fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. Refer to Section 1 , Powertrain Control Software, Fuel Trim for more information.

See Possible Causes for DTC P0171.

See Diagnostic Aides for DTC P0171

 

[Insane451]

I understand what the codes mean what I want to know is why it would be gone for over a week after cleaning the MAF and driving over 1500 miles, I know it doesn't take that long for the computer to reset. Is it possible my MAF is going bad? That is the only thing I did was clean the MAF and it seemed to be fine for that long trip and for a week and a half. I have no rough idle no surges no other symptoms that point to vacuum leak or not getting enough fuel.

 

[GaWag]

I fought these same codes. Intermittent check engine light. Cleaned and replaced maf. No vacuum leaks. No cracks.

In the end, the solution was a 10 dollar fuel filter. Once I pulled it, more black crap came out than fuel. I had over 270,*** miles as well. Drive like a champ afterward. If you've never change it, it's an easy and cheap fix. Should be done anyway.

 

[Insane451]

Thank you I will look into a fuel filter. I just got the truck last spring and I don't know if the fuel filter has been changed. If any one else has any other advice I would love to hear it.

 

[american steel]

look at your vacuum hoses and valves.

 

[Insane451]

I've checked for vacuum leak and there isn't any.

 

[Yudaman]

Start with the fuel filter. A clogged filter could easily cause lean conditions.
Besides, who knows when it was changed last...

 

[Insane451]

Ok so far what I have done after the light came back the second time is clean the MAF again replaced fuel filter, the old one looked like it was still new. I've looked for vacuum leaks, couldn't find any. The light hasn't come back on yet but it did take over a week for it to come back on the first time. If the light comes back on I think I'll replace the MAF. Is there anything else I should look into or check? It's just a waiting game right now to see if the light comes back.

 

[Insane451]

Ok it has been 2 weeks and one day since I posted and today the light came back on same codes. I cleaned the MAF and had the fuel filter changed in those 2 weeks. I know it doesn't take that long for the computer to reset. In those 2 weeks we had warmer weather in the 40s and 50s then the other day it dropped to below 30s again and now my light is back on. So I'm back to where I was before thinking it's either a MAF that's on its way out but still works off and on or its related to how cold it is. Every time the light comes on its below freezing and stays off when it's above freezing. Now that may just be a coincidence but it is what's happening. I'm still open to suggestions please help.