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.

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.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

My car died while I was driving and I can't get it started again. Fuel is being pumped and I have spark. What could be the issue?

It is possible that the timing belt has slipped or is broken which would cause loss of compression. You can check cylinder compression to get an indication of that. Also, you should check for fuel from the injectors, not just...

How long can a car run like when driving back and forth from work when battery saver mode is on? I plan to have it checked after w

The primary function of the battery is to start the vehicle. Once it is running, the alternator provides the electrical needs of the engine, lights,radio,heater,etc. If the alternator is faulty and not producing power, these systems will draw power from...

What does it mean if the "O/D Off" light comes on while driving? 1999 Ford Explorer

Hi there - first thing to check is for correct fluid level in the transmission. If fluid level is correct, the most likely culprit here is a bad vehicle speed sensor. A bad sensor can cause the transmission controller to...

Related articles

A Buyer’s Guide to the 2012 Ford Mustang
The The Ford Mustang has been an iconic vehicle for half a century, and its latest styling and updates only make it more attractive and more popular with American drivers. While its exterior may not be quite as eye-catching as...
The Best Used Cars to Buy If You Need a Lot of Trunk Space
Many Many people focus more on interior room than cargo carrying capacity. That’s natural if you have a large family or regularly carpool, but what about drivers who need to carry a lot of stuff most of the time and...
The Best Used Cars to Buy If Your Kid's On the Soccer Team
If If you are a soccer mom (or dad), you know that you need a lot of space to transport your budding World Cup contenders, along with their gear. From time to time, you can also expect to be bringing...