2001 Ford ranger 4x4 4.0L SOHC V6
So I have had this code for about a month now and I need to get rid of it ASAP so I can get rid of the truck. Okay so can someone who has experience with this code help me? Or anyone who may know the reason. It started out p0171 and p0174 lean in bank 1 and 2. I changed the intake manifold gaskets(lower) and the p0174 went away, but not the p0171.
It idles a little rough, but not too bad, when I accelerate it doesn't seem to have any power anymore, and it drives very sluggish. It is very annoying
The code came and it all started happening after not driving it for about 4 days.(Truck was running perfectly fine before I left it)
I have already done the following...
- checked all vacuum hoses (no leaks at all)
- Cleaned MAF sensor
- Intake manifold gaskets
- new pcv valve

I've been told it may be the fuel pump dying or the fuel pump regulator is bad(I have yet to do a fuel pressure test)
- may also be clogged injectors?
- bad o2 sensor (wouldnt it give it's own code and not cause these kind of problems?)

I've spent countless hours trying to figure it out and I don't want to keep buying things that won't fix it.
If someone had these symptoms with the same code please let me know what you did to fix it!

I found this looking online for the code.

Possible causes
- Intake air leaks
- Faulty front heated oxygen sensor
- Ignition misfiring
- Faulty fuel injectors
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Faulty Mass Air Flow (MAF) sensor
- Incorrect Positive Crankcase Ventilation (PCV) hose connection

Any feedback helps! Thank you

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Authentic Ladies

If you have an 01+ 4.0 with lean codes (PO171 and/or PO174) look here!

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2021 F150 5.0 Screw

Past:18 F150 2.7, 16 F150 5.0, 14 F150 5.0, 07 F150 5.4, 03 Ranger 4.0

Master Certified Ford Parts / Warranty Admin

I had this same problem but mine was a bank 1 and 2 sensors.
My list of thing I had to fix to clear the code:
Broke MAF sensor
O2 sensor
Fuel filter (helped the idle problem perfectly)
PCV valve

There was something else but I can't remember it at the moment.

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97 xlt 4x4, 4.0 auto

Just had the same codes, replaced the IAC solenoid.

I had both for a while and it ended up being my fuel pump assembly. 98 4.0

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Check the elbow for the pcv valve.

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1999 Ranger 4.0 and extreme Snap-on tool fetish

X2 on the elbow by the pcv. It's on the back side of the head so it's kinda hard to see. The elbow gets hot, old and brittle. Be careful with the pcv. I broke mine while changing the elbow. Almost lost it in the valve cover.

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2003 Ranger FX4 level II. 3" BL, 33x12.50 GT Radial Mud Claws, Custom front and rear bumpers with winch hookups, custom flatbed, with hi-lift, and full size spare mount, 12,000 lb winch mounted under bed, Electric fan, and of course a flowmaster.

+1 on vaccum leaks! replace all the lines while you're in there