Assume you have the 3.0l engine?

P0171/P0174 is almost never caused by a bad sensor, it is more often than not caused by intake air leaks. Contributors can be Intake Boots, CCV and Hoses, DISA, Fuel Pump.

You NEED to buy OBDFusion so you can provide warm idle Fuel Trim and Freeze Frame data. This is where to start to get an idea as to what is going on for sure.

__________________
2008 4.8i Black with Tabacco. Black Y-spoke wheels and shadowline trim.