A new problem

[Jim Tarr]

I replaced the thermostat with no problems. A little tight working area but all in all not too bad. Thanks for the advice. Now it's throwing two codes. PO171 and PO174. Bank 1 and 2 are lean. Would that indicate a vacuum leak? Is there anything obvious to look for or perhaps re-do my assembly proceedure? Thanks for any ideas you may offer. Jim:angry:

 

[Mark K 2]

Vacuum problem. Check vacuum lines near the thermostat housing. You may have bumped one or forgot to connect it.

 

[Jim Tarr]

Yep....I figure that I must have done something to cause this. I'll have to go back over my steps and hopefully correct the problem. Thanks,.....Jim

 

[swshawaii]

P0171 & P0174 4.0L SOHC's Sport/Sport Trac (PCV Elbow)

 

[Mark K 2]

P0171 & P0174 4.0L SOHC's Sport/Sport Trac (PCV Elbow)

https://www.explorerforum.com/forums/showthread.php?t=314670

I changed a valve cover gasket and missed a vacuum line and got the same codes.

 

[Richard Toms]

I had this happen to me on mine. Replaced just about everything, just trying to figure it out. For what I did, motor should be pretty much brand new...

PCV Elbow and Line: They were bad anyway, replaced.

MAF: Tried a new one, didn't make difference, returned it.

Throttle Body, MAF, Intake: Cleaned, no difference.

Upper and Lower Manifold gaskets: Replaced, no difference.

O2 Sensors: All of them changed out, no difference.

Spark Plugs and wires: No difference, but needed done anyway.

Coil pack: Had a Screamin Demon, and it was probably time to change it. Got a OEM one, and codes went away. Haven't had one since.