Hi,
I have a 1999 Ford Explorer with the X vin # 4.0.
I keep getting codes
PO171 & PO174 about every three to four hundred miles.
I have check everything I can think of, Fuel Pressure is good hot and cold . all vacuum lines good , evaporated system all good PVC system is good.
I replaced the fuel filter when it first came on and thought that would fix it being it was almost stopped up .
I checked everything I know to check for this code . Has anybody run into this . All the onboard moniters will signal OK even with the codes set.
Maf sinals and pressues are good through out all my testing when road testing.
Any body got any ideals or have run into this before??
Alvin