06 5.4 in a Super Duty....

The engine runs fine. on my way home from work... cruising at 45 mph my yellow check engine light came on....

I ran up to the parts store I am runnin lean on both banks the code reader says

PO 171 & PO 174

Any ideas ? I will start lookin for vacuum leaks tomorrow eve after work.

The engine runs smooth, and has power. It acts no different. Exhaust smells normal.

 

Make sure there are no leaks around air filter gasket and none leading to engine intake. Then i would take out and clean maf sensor with maf cleaner only. Then i would start engine let it idle down and spray carb cleaner around all vac lines and pcv line and around intake from idle air control to air filter. If no change in engine idle then no leak. Then i would reset ses light. If that doesnt correct it check that wires are all getting proper voltage and ground to maf sensor. You may have bad maf sensor but usually just clean it. Just did same exact thing bc of same code on my expedition. Fuel mileage was suffering too. Cleaned maf and tested for leaks and now all is well. Good luck

 

I'm having the same issue. I have replaced MAF sensor throttle body motor and throttle body gasket the vacuum lines from the break booster to the other side of engine compartment, the vacuum line elbow at the back of the motor the the f150 ' s were recalled for. (I have an 06 F250 5.4 too) the only thing I can think of is to replace the intake manifold gaskets. Have not found any vacuum leaks other than the elbow in back of the motor.

 

Mine was simply a dirty MAF.

Make sure you reset the computer or your check engine light and codes will remain.

I disconnect the battery, then connect the pos and neg cables together for 20 min, then separate and reconnect them to the battery. This wil reset to factory settings. I then drove to and from work, 25 miles each way gives the computer time to complete atleast 1 cycle.