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Code P0171 (Fuel System Too Lean – Bank 1)

Tiny
LINDA OLIVER
  • MEMBER
  • 2005 FORD FOCUS
  • 2.3L
  • 4 CYL
  • 2WD
  • MANUAL
  • 143,000 MILES
Check engine light came on I had a diagnostic ran on it and came back with the code P0171. They told me I need a vacuum control assembly valve, $217.00, but also says a broken hose on vacuum runner valve? Is this the same part? And upon further inspection we found that there is a large crack in the air breather housing which had been duct taped, the tape has come loose and I am wondering if this could have been the problem the whole time? Can you help me, as I am not able to keep pouring money into this with hit and miss sensors and such? I am unemployed at the moment and just cannot afford to. Any advice would be appreciated. Thank you.
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Wednesday, July 27th, 2016 AT 2:46 PM

9 Replies

Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
Any air leaks in the snorkel between the MAF and the throttle body can definitely cause a P0171. I see this code a lot on Fords and it ss nearly always a vacuum leak in a rubber hose or connector. We use a smoke test to locate these leaks.
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Wednesday, July 27th, 2016 AT 2:54 PM
Tiny
FREEMBA
  • MECHANIC
  • 1,152 POSTS
Be sure to check the PCV (positive crankcase ventilation) hose and valve for leaks (it is fairly common). The PCV valve connects to a hose (about the diameter of a nickle) between the throttle body and a larger hose underneath the intake manifold. It can be accessed from the front of the engine.
Also, there have been cases where excessive heat has caused the intake manifold to warp, thus causing a vacuum leak. However, do not remove the intake manifold unless a smoke test indicates that it (or its gasket) is at fault. Then use a straight edge to check it for warp-age.
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Wednesday, July 27th, 2016 AT 3:44 PM
Tiny
LINDA OLIVER
  • MEMBER
  • 12 POSTS
They performed a smoke test when they did the diagnostic, but would that even detect a leak in the PCV valve since it is behind the manifold where you cannot see it? And one more question if you can answer it. Is that vacuum control assembly valve an electronic part? And is it the same thing as a vacuum runner valve? Thanks for your help.
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Wednesday, July 27th, 2016 AT 9:35 PM
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Yes, it would. It would just be harder to see.
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Saturday, July 30th, 2016 AT 9:20 AM
Tiny
LINDA OLIVER
  • MEMBER
  • 12 POSTS
Just an update to let you know what we found, finally! After changing MAF sensor, twice, replacing a vacuum control assembly valve, and resetting the computer, the car still would'nt run, another $189 later. So a friend removed the air filter housing, which is supposed to be a lifetime filter, but is only good for around 150,000 miles actually, and found a crack in the bottom of the housing had allowed all sorts of debris to clog the air filter, which wouldn't let the motor breathe. So, for others with this same problem, check your filter first! Save yourself hundreds of dollars and do this first! Also to replace the factory filter is around $200, so I just did away with it and installed a clamp on K&N filter instead, for $46.
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Thursday, September 29th, 2016 AT 8:13 PM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
I have to disagree with you. There is no such thing as a "lifetime filter". Air filters have to be replaced on a regular basis. Also, a clogged air filter will not cause lean codes in the engine, however, using an oil soaked K&N filter will clog up your MAF and that will give you a lean code. I do not recommend K&N filters. The company makes numerous benefit claims that are just factually not true. They actually have more detriments than benefits.
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Friday, September 30th, 2016 AT 4:25 AM
Tiny
LINDA OLIVER
  • MEMBER
  • 12 POSTS
I appreciate your opinion, but I haven't had any problems since installing this "option" to the factory air filter, no codes are being presented, and the car runs better than it ever has, so I will drive it this way and see how long it takes before the MAF gets clogged, and if it does, I guess I will pop it out, clean it and reinstall it, but as for now, it seems to be doing fine. The only reason I posted an update was to hopefully save someone else with these same kinds of problems the headache and expense I had to go through.
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Sunday, October 2nd, 2016 AT 6:46 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,904 POSTS
I have a 2005 focus that has 51,000 miles and they come with a lifetime air filter from the factory, you cant even open it to look at it. Not the best idea because an air filter gets dirty no matter what so I appreciate your response. I will look into replacing the filter.

Thanks again for getting back to us.

Best, Ken
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Tuesday, October 4th, 2016 AT 8:58 AM
Tiny
LINDA OLIVER
  • MEMBER
  • 12 POSTS
I'm glad that the information I have posted here may be able to help you, please let me know if it does! Thank you.
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Wednesday, October 5th, 2016 AT 6:46 AM

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