Q: F150 running rich

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.