P0171 P0174 all conditions

Hello,

I know I have read a few posts here and in the F150 forums that give lots of detailed information on these codes. However, I just can't get past them, and was seeing if I can get any help. Here are some of the things I have done to start off with:

Cleaned MAF (and replaced)
Changed PCV hose with bad rubber boots
Changed DPFE sensor and hoses that had deteriorated
Changed fuel filter twice now
Smoke test came back with no visible leaks
Seafoam in the fuel tank a few times to see if that would clean anything out
fuel pressure within specs, although it goes to 0 after turning engine off. Does not have starting issues otherwise
Can verify that the O2 sensors are working as intended with simple tests.

I can tell you it is lean all the time - at idle and while driving down the road. The only time it goes down to a rather acceptable level is when I am decelerating. I am using a Bluetooth ODB-II sensor with Torque app, so I can provide any information you may need. I just want to get this fixed so it can pass state inspections.

What was the fuel pressure reading?

The "0" reading is a problem but not the cause of your issue.

It is the fuel pressure reading, yes. I figured as much, but just put that out there. I am sure the fuel pressure being normal (albeit closer to the bottom end, but not enough that it goes too low under load) is saying that is not the problem.

And since I had to look at the notes I took, it was around 38psi, not going any lower then 35.

I would expect the check valve in the fuel pump assembly has failed causing the drop to "0" psi with engine off. It may also indicate a worn pump. I usually plan on replacing them at between 150 - 200k miles.

If both banks are lean then:
1) search for vac leaks after the throttle body
2) swap intake gaskets and inspect the intake manifold for cracks

When I changed out my sparkplugs last month, I left the PCV inlet pipe off the driver's side valve cover grommet and that gave me a 0171/0174 code. There's so much junk in that area I over looked it. Didn't find it till I smoke tested the intake. But it showed right away, and I kicked myself. I would've thought your smoke test would've definitely showed any vacuum leak. So, any leak downstream of the MAF sensor will probably throw the 0171 and/or 0174 code.


-Mike


http://www.evaporativesmokemachines.com/

If you need a good smoke machine that won't break the bank ....

On my '04 about a month ago when it began to get cold over night it threw a PO171 code. Still starts, idles and runs fine. I cleared it and it came, back did this a few times...it would last maybe a not even a hundred miles and threw the code. Last time I reset the ECM so it would relearn the parameters and it has been fine over 200 miles and quite a few starts.