2002 Ford F150 fuel issues


Our 2002 Ford F150 continues to have the “check engine soon” light come on. Diagnotic shows codes PO171 & PO174. We have had the fuel filter replaced, fuel pump replaced, gas cap replaced, fuel injectors cleaned and vacuum lines replaced. After the new gas cap the light stayed off for over a month but is back on.

HELP!!! Any suggestions of what else our mechanic can try. We are stumped.