Two guys i work with have the same truck, both 2010 F150 5.4l engine. Both trucks were getting 16-17mpg and now their getting 10-12mpg. also if the truch sits for 8-10 hours over night with temp. averaging -2 degrees celcius they barely and sometimes wont start any ideas????? Ford has changed all sorts of sensors but cant figure out what is going on.

 

What has Ford done, - which sensors ? Where do you purchase your Petrol ? What's 2 degrees Celsius mean ? We are Fahrenheit familiar in the USA, ehh.

So has Ford done a fuel system diagnostic ? Did they rule out a regulator problem ?

 

2 Degrees Canadian and most of the rest of the world is about 35-36 degrees American. 0 Canadian is 32 American so using that as a baseline..
Sounds like bad Canadian gas to me.

 

Correct about the temp. they changed the O2 sensors And the mass air flow sensors To try diagnos the fuel system they instaled a gauge under the hood to see what line pressure is and it is around 60 psi at idle the fuel was tested and it has 5% ethanol blended.

 

I'd take a shot at switching fuel supplier..

 

Sorry should have mentiond that they have tried other stations. It has been going on for two weeks or so fueling up every 2-3 days. Even if it was a bad tank i think it would be through the system?

 

What has Ford changed exactly? how many miles are we talking about on these trucks? Seems very odd to me this problem is affecting 2 different trucks and all.. Have to be something they have been sharing..

 

just those O2 sensors mentioned he just talked to the service manager the fuel system in the pcm is reading that the fuel is 56% ethanol wich makes the truck run very rich. This truck has 83,000km 0r 51,500 mi The other truck was traded off today at 97,000km.

 

No chance of mistakenly putting in E-85? That would cause..

 

No E-85

 

Seems to me that the flex fuel engines have a sensor that measures the ethanol percentage somewhere - logic tells me that perhaps that sensor is bad.

 

Dealership has changed the fuel pump and truck runs great getting good mileage again.