I had the exact same codes on my 2000 Navigator with a 5.4L eng just today. It was a vacuum on the top of the motor. The hose had deteriorated and caused an associated hissing sound and rough idle. Used a little duct tape, ops check good, no return faults.
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Lean bank 1 and bank 2 , and throttle actuator system fault. Check reason for lean codes 1st, vacuum leak(s), air inlet boot and hoses, or low fuel pressure / clogged filter. Repair as needed then clear codes and recheck .
This is a tough one could be mass air flow sensor ,oxyegen sensors,a fuel filter. a vacum leak, a pcv valve if i missed anything just google po 171 &174 look for fix ya this issue has been addressed many times first check the vacum lines includeing the line on the pcv valve for cracks or splits in the lines .I would do the fuel filter if it hasnt been changed in the last couple of years , if still a problem the MAF sensor if your happy with my advise please leave me with great feedback
Common fault is leaking gasket on intake manifold towards the back, do you have the following symptoms - uneven idle - sudden cut out on idle but starts up again with no problem? If so you will find a leak on the inlet manifold. The codes show a leak after the MAF- so this is the area to check. Hope this helps.
There is a problem somewhere in the system relating to oxygen content coming from the intake manifold and or fuel delivery system. from experience iv done alot of intake gaskets cause of these 3 codes
po174,po175,po171 to find the problem i use a smoke machine with a cold engine, smokes comes right out of the intake gasket im sure theres other ways to chek it too