I had the dealership check it out and they said the MAF threw a code (but it never lit the check engine light). I've never replaced that sensor on this model truck - what are the tricks I need to know to do it?

 

I replaced the MAF with no change.

I guess it's back to the drawing board. Is there a way to check the EGR without pulling it? What about the O2 sensors (should I be checking voltages)?

 

If the O2 senors end up being bad then Ford will have to pay for them to be replaced. All or the emissons items are under warranty for 8 years or 80,000 miles by federal law.

 

But the EGR doesn't fall into that category (of being under 80k mile warranty), does it?

Any way to check the EGR?

 

Have you recalibrated the speedo? Your 245 tires are taller causing your speedo to read 1.833% too slow. That will affect your mpg both by the computer and if you figure it by hand. If nothing else changed but your tires that cwould definately be part of the problem.

http://www.1010tires.com/TireSizeCalculator.asp

 

1/4 of an inch in tire height would cause a 5 mpg drop in fuel mileage? Assume I drive at a constant speed (the site above says if my speedometer shows 58.9mph I'm actually going 60 mph) for 5 hours. This means I've actually traveled 300 miles but my odometer is going to show 294.5 miles. Assuming nothing else is affecting my gas mileage, say I use (just for an example) 15 gallons. I actually got 20 mpg but by calculation with the faulty odomoter reading I got 19.6 mpg. I've lost a lot more than that and I don't know where it's going.

 

fuel filter is my guess. it is common for most persons to not change their fuel filter even though it is a regular maintenance.

 

good idea pukemon...fuel filter is recommended every 30k....you might have gotten 1 bad tank and crapped up your tank and now your still suffering.

otherwise, I'd say it's the gas causing your problem. the higher ethanol content gas really makes the MPG drop

 

I've changed the fuel filter twice in the last 10k miles.

 

Regarding the power issue:

The truck seems slow to shift sometimes. Normally, like when I'm not pushing it, it shifts into Overdrive well before 70 mph. This morning I watched the tach and the transmission hung onto Drive and reached 3000rpm at 70mph and finally shifted into Overdrive.

Also, when at 70mph my tach should read 2000rpm on the nose. I've noticed several times the transmission will come out of lockup and the tach will jump up to 2250rpm (or thereabouts) when just cruising along, like there is a lack of power.

 

Just traded a 06 KR. It never cracked 16mpg on steady hiway driving. The
5.4 ran fine, transmission shifted fine. So figured 12-13 with city would
have been good. The new diesel is only doing 13 on the hiway

 

Diesel what ? I've talked to guys with 350 utility body diesel getting 17. Hopfuly you get more when it breaks in. I only get 12-13 out of my 2004, 5.4 4X4 scab.

 

Lots of post on the 6.4's poor mileage, The day brought it home was
only doing 9 on the hiway, after 2 resest of the reader. You have to
really light foot it to get 13. Some not reporting better after racked
up some mileage.

 

I'm reading that they need to remove the cab to do some engine work on the new diesel. They set it up that way. It supposedly only takes 20 min. I wanted to keep my 04 150 till the new diesel 150 comes out. I think it might be better to what till the bugs are out. The guys at the Ford dealer as of Mon. havn't even heard of a 150 diesel. I was looking forward to getting better that 20 mpg in a smaller diesel in a F150. I'll bet the new emission standard is messing with your mpg in your new diesel

 

did you have the trans/filter changed ? also did you change your tires..