I have a 1999 Windstar 3.8 L. Have the codes PO171 and 174.
I have codes PO171 and PO174. I have changed the MAF sensor, DPFE sensor, fuel filter and downstream and upstream O2 sensors. I reset the computer by disconnecting the battery. Codes came up after 60 miles of driving both highway and city driving. What else could it be causing these codes? Someone please help.
Those codes are usually caused by a vacuum leak, or unmetered air that is entering the engine after the MAF sensor. Check all your rubber hoses and gaskets. I usually run the engine and pop the hood and move some hose around to hear hissing, you can also spray some carb cleaner around suspected areas, if there is a leak, the idle will increase. If you can't find one , you can do a "smoke test" that can pinpoint the area of the leak.
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