PO171 & PO174 codes.

[Mike65]

Now that I finally got the Evap codes fixed a few weeks later the CEL comes on & I am like oh **** not again, but it was po171 & po174 codes banks 1 & 2 lean. When my wife starts the truck it starts fine & for a couple seconds will idle fine, then the idle drops off like it is going to stall then it comes back to normal idle & is ok. It drives fine with no hesitation, or stalling. Today I found on line that it could be a dirty MAF sensor so I pulled the MAF sensor & sprayed it with MAF cleaner & reinstalled it, It also said check for vacuum leaks so I sprayed the cleaner around the IAC, egr valve, & where the egr tube goes into the upper intake with no change, but tracing vacuum leaks on the 4.0 SOHC motor are hard to get at a lot of the vacuum lines that are under the upper intake. It also said low fuel delivery could also cause the codes as well as a bad DPFE sensor. The Explorer Sport has the 4.0 SOHC engine with about 110,000 miles on it. It also has a new fuel pump which I replaced last year for a no start cold problem, but the fuel filter is old. Where is the port to check the fuel pressure on the 4.0 SOHC engine?.

 

[rasouth]

The port should be on the passenger side and looks like what you inflate a bicycle tube with. I've got a '96 and that's where mine is located. A clogged fuel filter might cause those symptoms by restricting fuel. With the engine running you might try spraying starting fluid around the intake manifold. If idle speeds up there's your leak.

 

[swshawaii]

How to: Lean condition procedure
http://www.explorerforum.com/forums/showthread.php?p=2364255

2000StreetRod's Helpful thread list

 

[410Fortune]

After you do the fuel pressure tests, with a p0171 and po174 ona sohc engine, most likely your intake plenum O rings are leaking air
Plan to replace both upper and lower intake plenum O rings