So I have a 2008 F250 4x4 crew cab with the 5.4l triton. The truck sat in storage for two years and only has 100,000 km or 62,000 miles on it. So far Ive replaced, gas cap, fuel filter, air filter, fuel pressure sensor, spark plugs, coils and brand new high flow cats and new muffler.

It started to give me the usual triton problems within the first 1000 km I drove it for and that's when I started to put all of the above new parts into it. The truck definitely runs very smooth now but my issue is that the mpg never change wether highway or city? It stays consistent at 20l per 100km or 11.76 mpg. I'm wondering how this compares with what other people might be getting?

I've noticed that after I let off the gas, there seems to be a delay of about 1 second before the engine rpm actually decreases. I'm wondering if I have dirty or worn out injectors that are cussing issues for the pcm and that possibly that's why the milage never changes? Any help is appreciated.

 

have you inspected the brakes...? dragging brakes can do this...

2 years sitting is not good..

 

Second checking brakes. Also check parking/e-brake.

 

Wow I definitely never would've thought of that but I have noticed that the rear brakes will squeel like crazy and you've driven say more than 20 min, the rear brakes will sqeel but when the truck is cold, the brakes are silent with no noticable noise? So I guess it's heating up, expanding and causing drag?

 

If you are having sticking caliper or dragging pad issues, the rotor of the offending brake will look very shiny, almost like chrome. The wheel hub will be hotter than the other wheels when you first park after a drive.

 

Are you hand calculating the fuel mileage or using the Lie-O-Meter? Are the tire the stock size? Taller than stock tires will cause your miles traveled (Odometer) and speed (speedometer) to under report, which will also throw off the mileage calculations.

 

Mine is a 2v, but if I do mostly highway driving at 55-60 mph it gets around 15 to 16 mpgs. If I do a lot of city driving then it gets around 13 mpgs. It's a regular cab, manual with no upgrades, so it's on the higher end of the spectrum for mpgs.

 

Checked out the brakes and everything is fine. Just used some silicone lube and the rears are quiet now so that wasn't it.
​​​​​​ I'm going off of what the truck itself is saying as far as milage goes and the truck has stock rims and tires and gearing.
Was hoping that it was just the fuel injectors, $600 to replace them all isn't to bad and will pay for itself over time. Just don't want to do it if there's no possibility that it would help.

 

It sounds like you are trying to solve problems by throwing the parts store at them, which is only certain to drain your wallet. I don’t think the $600 for fuel injectors will pay for anything over time, those aren’t a normal maintenance item.

How is it idle? The delay after you release the throttle might be a sluggish idle air control valve. It’s pretty easy to clean, and you can even find a can of CRC cleaner at Walmart that would fit the bill. I would recommend pulling the IAC and taking a look there. I would not expect that to affect your fuel economy. Do you have access to a scan tool of any kind? If so, I would take a look at your fuel trims.

 

My 03 Mercury had the right front wheel hub bearing failure (could feel the heat emitting from the wheel) and when I got home, I jacked the right front and I was unable to spin the wheel . I'm lucky I made it home.
My 2011 E-150 5.4L, 45K, fuel mileage has dropped from 14.5 down to 12.8 MPG according to the Lie-O-meter.