Need help with P0171 p0174

[antihero214]

Im at a loss as to what is causing these lean codes.

so far i have:
replaced downstream o2 sensor
replaced iac (it was howling and truck was dying out at stops.)
replaced one verified leaking vacuum line.
replaced upper intake and fuel manifold gaskets.

ive smoke tested and used propane and carb cleaner. there is no leak.

fuel pressure is at 60psi running.

maf has been cleaned and tested.

where do i go from here.

 

[jeremysdad]

Engine? Auto or manual? 15 years old... Pcv elbow? Intake manifold gasket? Clogged fuel injector? How many miles?

Need something to work with other than lean bank one, and generally lean. Fuel filter? lol

 

[jeremysdad]

http://www.obd-codes.com/p0174

I bet your fuel pressure drops at rpm, or you were afraid of blowing yourself up with the propane. I assure you, as long as you have the hood off or your hair back, it's just one little 'whoof' and then it's gone.

 

[Dune Runner]

Back when I first bought my truck I kept getting these codes. I tested for leaks and couldn't find any. Took me forever to find the vent line for the EVAP system had come loose off of the top of my fuel tank. I snapped it back in place and all was good. Every time the truck would go into purge mode for the EVAP system it would throw a lean code due to it pulling in fresh air into the intake instead of fuel vapor.

 

[adsm08]

Replacing the downstream O2 sensor was worthless. It doesn't contribute, at all, to the determination of rich or lean.

You need to tell us what engine you are working on. Since you have a 174 it could be a 3.0, or either of the 4.0s.

If you replaced the upper intake gasket the lower could be leaking. A PVC elbow could do it, and the one at the throttle body of the 4.0 SOHC is a common failure point these days.

Now if you have a scanner that can do live data you can access the fuel trims, take some recordings, and do a little math to help figure this out.

At idle take short fuel trim 1 and add long fuel trim one. Then do the same at 2500 RPM. Subtract the sums from each other, if the difference is more than 15 points it is an air leak. If it's less the MAF is likely at fault.

 

[antihero214]

2000 ranger p0171 174

its a 2000 ranger auto 4x4. 4.0 ohv. it has 145,000 miles on it. i changed the downstream 02 because it intermittently would drop out and not change from 0 volts. as i mentioned before fuel pressure is 60 psi running and doesnt drop when raising rpms. I was also quite liberal with both the propane stream and the carb cleaner. the ohv doesnt have the pcv elbow that the sohc has. the fuel long term fuel trims are always in excess of 15, usually 25.0 when under light acceleration, under medium acceleration will drop to normal range, heavy acceleration ft can reach as high as 40.

 

[jeremysdad]

I digress...as of yet, I am undecided as to whether I am glad or sad that you didn't explode. There is a section here for Ford Techs. This is not it, from what I understand of the rules.

ADSM08: Y'all really should make a 'Ranger Rookie Ford Tech' section...or some such.

NEta: Sad. lol

#stilltypemysmilies

 

[antihero214]

ok im a little confused. im not a ford tech. just someone with a problem that has requested help.

 

[adsm08]

ok im a little confused. im not a ford tech. just someone with a problem that has requested help.

Ignore him. Anyone who uses hashtags clearly has no idea what is happening around him. It's even worse when doing it on a forum instead of Twitcher or Wheety or whatever it is.

 

[antihero214]

im beginning to think it is the lower intake gasket. i dont know what else it could be.

 

[Dune Runner]

Did you check the EVAP vent line coming off the top rear of the fuel tank?