po171 code help needed It's killing me

[kingoftheplanet]

I have a 1997 explorer sport 4X4 4.0 sohc that i recently (within 2 weeks) have put a new fuel pump,,fuel filter,,injectors,,valve cover gaskets,,air filter,,intake gaskets,,i also have cleaned the MAF and fuel pressure is in spec is at a solid 35 with vacuum line on regulater and 40 with it off..i did the propane vacuum leak check and cant find anything. cant hear a vacuum leak either..it only has the lean on bank 1 ,,PO171 code..after half throttle it bogs but after a couple seconds will start making power again..fuel economy is suffering bad...like 200 miles outta my last full tank....I'm mind boggled by this problem and am lost..i need help bad because its just eating me up,,and i know there are alot of professors of the explorer on this site..any help would be freaking awesome...THANKS IN ADVANCE :exp:

 

[kingoftheplanet]

Also forgot to add that it starts great and idles fine

 

[ragajungle]

too little fuel or too much air.... Could it be a stopped up fuel filter? MAybe when you changed the pump you stirred up a bunch of sediment? Perhaps one or more of the Fuel injectors is clogged on the left bank -- maybe something in the fuel rail...

 

[swetrid]

Could be o2 sensor, we see alot of these on high mileage that stop working intermittently when hot and cause driveability issues. That being said , make sure there are no vacuum leaks like the typical intake gasket problem.

 

[kingoftheplanet]

Everything is new and did fuel filter after doing pump..injectors are also new..if it was an o2 sensor would it give a code..cant find a vacuum leak to save my life either..im lost..with no direction..gonna have to take it to the dealer and let them sort it out i guess..lol

 

[kingoftheplanet]

Its the same when cold or hot. Doesn't seem to make a difference..

 

[kingoftheplanet]

Really wish i had a smoke machine..

 

[2000StreetRod]

Passenger side only lean

Low fuel pressure due to pump or filter should affect both banks. Same is true for a leaking EGR tube O ring, main intake tube leak and the main PCV valve tube leak.

P0171 System too Lean (Bank 1)
Look for a vacuum leak specific to the passenger side:

Disconnect vacuum supply hose going to variable intake system (VIS) vacuum solenoid and plug. The VIS only starts to activate when engine speed approaches 3,000 rpm.

Disconnect vacuum supply hose going to heater water control valve and plug.

Disconnect vacuum supply hose going to the EGR vacuum regulator and plug.

Check the vacuum hose going to the vacuum reservoir located in the passenger side front under the air filter mount.

Check the hose from the PCV valve "T" to the passenger side rear of the upper intake manifold.

Check the hose connected under the passenger side of the intake manifold about midway front-to-rear that connects to a "Y" from the driver side and then goes to the fuel vapor management valve located below the battery tray.