Q: F150 running rich

asked by on October 11, 2017

My 2008 F150 5.4 4x4 with 230,000 and a cold air intake is running rich (P0172/P0175), poor gas mileage/power and poor acceleration. I have replaced the mass air flow sensor, fuel filter and O2 sensors were replaced over a year ago. The truck also struggles sometimes on inclines and hesitates on cold take-off's plus poor acceleration.
The spark plugs were changed at 165,000 and the oil is changed every 5,000. Thanks in advance

PJ

My car has 230000 miles.
My car has an automatic transmission.

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The most common causes of too much fuel being delivered are: a dirty mass air flow sensor that overstates the amount of air entering the engine; a faulty oxygen sensor; a faulty coolant temperature sensor (the temperature signal is a part determinant of injector pulse width); a leaking fuel injector allowing too much fuel to enter the combustion chamber; a faulty fuel pressure regulator; a vacuum leak; a stuck open thermostat; worn spark plugs; and so forth. Given the other "symptoms" you are reporting, and given the high accumulated mileage, as an initial step I’d remove all the fuel injectors from the fuel rail and send them to a lab such as Mr. Injector (there are others out there, too) where they will be tested, cleaned, the tiny internal filters replaced, and so forth. Note that you want the injectors checked for leaking. In addition, you can request a check engine light diagnostic during which a certified mechanic from YourMechanic would test the appropriate individual vehicle components or sub-systems (often a sensor, circuit, and the like, as noted in the list above) to pinpoint the fault that has caused the codes to set. If you have further questions or concerns as you decide what to do, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.

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