codes p0171 and p0174, Need help ASAP!

[black97xlt]

for the last month the truck has been acting strange plus upon accelerating up a hill or put under load it stumbles and tries to fall on its face. both codes are (System Adaptive fuel too lean banks 1 and 2). this weekend is my only chance for a while to fix it and I need it done asap. Anyone have any ideas what is causing this thing to lean out enough to throw these codes?

 

[1stGeExpedition]

Although, there are a few causes the most common is the PCV Vent Tube which is located in the middle of the intake near the firewall (behind the throttle body) & runs from the intake to the passenger side intake manifold.

If you navigate over to the "how to section" there's a writeup on this issue.

There's also a few YouTube videos out there...

This one is very detailed and is instructions on changing your intake gaskets... I just like his instructions and this is not necessarily your issue. It'll help you understand what to remove to gain access to the rear of the intake and what tools you'll need.

Ford 5.4L 2v Engine Intake Gaskets P0171 P0174: http://youtu.be/IJJTlDrCaUQ

This one is the actual pcv tube replacement...

F150 PCV Tube Replacement: http://youtu.be/7UL6yST1aUY

On my truck (2000 5.4 Expy) the vent tube was the last thing I checked because I was getting other codes along with the p0171 & p0174.

The other codes were...
p0357 p0308 p0161 and p1506

I changed plugs, coils, o2 sensor, and fuel filter before I checked the pcv tube.

Once I cleared out the other codes and changed the pcv tube my truck has been running like a champ.

If you get into the pcv tube replacement or repair I would clean out the throttle body, iac valve (behind the throttle body), and your intake. All of that stuff tends to get caked up pretty good.

Hope this helps.

Here's what mine looked like once I got it out...



Sent from my SAMSUNG-SGH-I337 using Tapatalk

 

[bedrck46]

H41 DTCs P0172, P0174, P0171 AND P0175: FUEL SYSTEM AT THE CORRECTED FUEL TRIM
Diagnostic Trouble Codes (DTCs) P0171 bank 1 (Cylinder 1) and DTC P0174 bank 2 indicate the fuel/air ratio is too lean. The fuel trim system is at the rich correction limit.

DTC P0172 bank 1 and DTC P0175 bank 2 indicate the fuel/air ratio is too rich. The fuel trim system is at the lean correction limit.

DTCs HO2S Reference list:

HO2S-11 = DTCs P0171 and P0172
HO2S-21 = DTCs P0174 and P0175
Possible causes:

Fuel system

Excessive fuel pressure.
Leaking fuel injector(s).
Leaking fuel pressure regulator.
Low fuel pressure or running out of fuel.
Contaminated fuel injector(s).
Vapor management valve (VMV) leaking.
Induction system

Air leaks after the MAF.
Vacuum leaks (vacuum lines and gaskets).
Restricted air inlet.
PCV system.
Fuel purge system.
Improperly seated engine oil dipstick.
EGR System

leaking gasket.
Stuck open EGR valve.
Leaking diaphragm.
Base engine

Oil overfill.
Cam timing.
Cylinder compression.
Exhaust leaks before or near the HO2S(s).
Check intake air system for leaks, obstructions and damage.
Check air cleaner element, air cleaner housing for blockage.
Verify integrity of the PCV system.
Check for vacuum leaks.

 

[black97xlt]

That's quite a list of things to check. the intake manifold gasket is less then a year old. probably needs plugs. has new accell super coils. have replaced almost every vaccum hose under the hood. I have checked the pcv. It has always had an exhaust leak just b4 the passenger side o2 but never seemed to cause an issue.

 

[04SVT]

Does it have a cai?

 

[black97xlt]

yes, aem. Why?

 

[04SVT]

Check the fittings and couplers

 

[black97xlt]

everything seems pretty damn tight.

 

[04SVT]

Any vacuum reference lines from the underside?

 

[black97xlt]

what do you mean?