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How do I know if the MAF is causing a P0171 code?       #: 2244
 Moderated by: Mike69, MaDMaXX
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 Posted: Mon Sep 7th, 2020 03:41 am
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wh23g3g
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I keep getting a P0171 code at random times. I'll clear it and then it comes back in 20 miles, 100 miles, or 400 miles. No specific amount of time. I attributed it to the higher mileage on the motor and the long idling I've been doing during lunch breaks from work. Since you have to eat in your vehicle now. It's been really hot out so I've been using the A/C non-stop and while idling during lunch breaks. Sometimes up to 30 minutes everyday. It drives well and idles good. It's in proper tune for a 200,000+ mile engine. Not sure exact mileage on the engine it was replaced at 228,000 with a supposed 50,000 mile used motor. The truck now has 402,000 miles on it. All service is up to date, no vacuum leaks evident. Fuel pump assembly is only a couple years old now. Only 20,000 miles since timing belt, plugs, wires, coils have been changed. Even less so on the EGR system. Is there any of the PID information that would make it easier to narrow down? I've replaced both 02 sensors since they're kinda old. I replaced with Motorcraft. Everything ignition and electrical is Motorcraft parts. Two or three years ago I went through and changed every electrical and emission item to new Motorcraft parts. It ran the best it had since it was new after that. Could it possibly be nothing wrong but just the extensive amount of idling now doing?



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 Posted: Mon Sep 7th, 2020 12:19 pm
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Tsquare
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That is supposed to be the upstream O2 sensor letting you know the air/fuel mix is off. My guess is ether MAF or injector.



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 Posted: Mon Sep 7th, 2020 02:02 pm
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it is not your amount of idling, you should be able to idle for a week if you want to
Is this a 4 cyl? 3.0 or 4.0?


P0171 means a lean condition only in one bank, one side of the engine
Typically that usually rules out anything that effects both sides of the engine like the MAS, intake air leaks, etc since they would effect both sides, typically, not always. The Po174 code may not be far behind
Lean condition means the computer has seen more 02 in the exhaust on that bank then expected and it has already tried to correct it by adding more fuel, still the condition is lean. It has occurred enough times to set a code.

With those miles and the work you have done I would suspect:
failing injector
wiring at the 02 sensors you replaced (always good to go back and check the work you have done)
exhaust leak on bank 1 side
or failing pcv valve (but again that usually effects both sides)
Cleaning the MAS NEVER HURTS


from OBD2.com:
"The MAF (Mass Air Flow) Sensor is dirty or faulty Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. 
There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry. 
There could be a vacuum leak downstream of the MAF sensor 
Possible cracked vacuum or PCV line/connection 
Faulty or stuck open PCV valve 
Failed or faulty oxygen sensor (bank 1, sensor 1) 
Sticking/plugged or failed fuel injector 
Low fuel pressure (possible plugged/dirty fuel filter!) 
Exhaust leak between engine and first oxygen sensor

Read more at: 
https://www.obd-codes.com/p0171



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 Posted: Mon Sep 7th, 2020 09:12 pm
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wh23g3g
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It's the 2.5 which I just changed both O2 sensors out. I used the Motorcraft brand. The sensor 1 tip was really white. I'm wondering if it's the AFE open element air filter. My original air filter housing is cracked so I got the AFE which I liked because it still retains the original air intake hose and sensor. It uses the dry type air filter so there's no oil. I've got that FORSCAN software. Is there anything I can watch to get a better idea of what might be causing it?



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 Posted: Tue Sep 8th, 2020 02:50 pm
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I use AFE dry filters as well, they work wonderfully
Your MAS could cause this for sure as the 2.5L is a inline 4 cylinder so there is only one bank
Have you tried cleaning the mas?
any intake/air leaks after the mas?

check wires to the 02 sensors you replaced, make sure all the pins are there, have not been pushed back and are clean



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