P0171 and p0174
.Both banks too lean ....http://engine-codes.com/p0171_ford.html .....and http://engine-codes.com/p0174_ford.html ..usually the MAF dirty of failed Or a vacuum leak. See http://www.smogtips.com/smog-question/1018/What-causes-Trouble-Code-P0171-and-P0174-Ford-Expedition
There is another article at: http://troubleshootmyvehicle.com/ford/4.6L-5.4L/troubleshooting-p0171-and-p0174-page-1 ..... that may help too
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