It was actually the PCV hose from the back of the intake to the passenger-side valve cover. I'd seen others post about this as well & they were 100% correct. After 5 yrs that hose (plastic) collapsed at the 90 degree elbow as well as having a hole in it. It was sucking air causing the "lean fuel" code. Swapped ~25 part & runs good as new now!!
You may have an exaust leak or the catalytic converter may be bad.
Vvbbb
SOURCE: What are the descriptions for
P0171 - System too Lean (Bank 1)
P0174 - System too Lean (Bank 2)
They have to do with fueling the engine. Usually when a car is running a less-than-optimal fuel mixture, it's traceable to O2 sensors, mass airflow sensor, or sometimes a coolant temperature sensor. These all have a direct effect on the fuel mixture. If your O2 sensors have been in the car for more than 60k miles, I'd change them first, as they have the biggest impact on fuel mixture. I don't know what year your car is, but if it's 95 or older, there is only one sensor per bank of cylinders. If it's 96 or newer, you'll have four - two before the catalytic converters, and two after them. The ones you'd want to change are the pre-cat O2 sensors, closest to the engine. These are used for determining fuel mixture. The post-cat O2 sensors are there for monitoring the cats' efficiency.
SOURCE: po171 po172 po174 po175 ???
If the fuel pressure was low enough to give lean codes then u would have a loss of power that you would easily notice, you say you checked for vacuum leaks, did you use a can of carb spray or a bottle of propane? it only takes a very small leak to trigger the codes, spray carb spray around the intake area, see if the engine sound changes, this will indicate a leak,
SOURCE: 1996 ranger 4.0 codes po171 and po174 come up on the screen
Check for vacuum leaks, especially the intake manifold gaskets. If those are o.k., clean the Mass air flow sensor.
SOURCE: code po171 and po174. fuel bank 1 & 2
From Twitter by @carpartslocator.
@car_problems oxegen sensor oar the airflowmeter.but i do not know what kind of car you have i am gessing ford....??
Good luck.
SOURCE: code po171 7 po174
your computer is reporting bank 1 and 2 too lean, usually caused by the mass air flow (MAF) sensor, you can usually clean this sensor and reset the light. Clean it with electric cleaner or brake cleaner, make sure it is dry before reinstalling, also take care not to damage it. Hope this helps, let me know
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Same problem with an1997 E2505.4L V8
I've also got an '03 Eddie Baur 2x2 Exp with ~88k miles. Wife got the P0171/0174 codes the other day. Cleaned the MAF with no luck so going to try the other suggestions I've found on the Net like checking for a hole in the PCV 90 degree elbow on the back-side of the intake. Seems to be a common issue/fix.
97 merc grand marquis...same prob
o4 mitsubishi endeavor , po174 system too lean
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