I have a code po174 system too lean that keeps coming on on my 2003 Lincoln navigator, I've changed all o2 sensors, a vent hose, checked maf, sprayed carb cleaner lookin for leaks an can't find anything, anyone else had this problem?
Other causes are: Plugged fuel filter, low fuel pressure (bad fuel pump) bad fuel regulator or leaking regulator, dirty injectors, leaking vacuum line, pcv leaking, stuck or bad egr valve and bad maf.
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