I have a 2002 Ford F250 with a newer V10 motor, Ford dealer rebuilt my motor 30,000 miles ago and truck only gets 6-7 mpg so I was wondering if those chips they are advertising work and if they do which do I need? Also lately the engine has been surging,when it's idling or when I'm stopped at a light and truck is in gear it will suddenly surge between 500-750 rpms then go back to normal then surge again and again,,Any ideas? I am not a mechanic so I'm at my wits end,,I have a K&N filter,new fuel filter and pump.

 

Any codes ? Have you checked the mass air flow sensor ? If over oiled , the K&N can damage the mass air flow sensor . Just a thought .

 

So how many miles are on the truck? Maybe oxygen sensors need to be replaced.

 

Surging, I would clean the mass air sensor. Use the correct stuff. Which is called somthing like mass air sensor cleaning.

What points me to this is your KN air filter. Small amount of will deposit on the sensor causing surging. I have had this problems in the past and will never again use a oiled filter. This could also reduce your MPG.


As far as MPG go. What size tires, Lift kit, 4x4, City Driving?

 

Would bad O2 sensors be accompanied by CEL and/or codes?

 

Have a '09 250 SD 3V V10 and experienced some of your problems, maybe this will help you. Have an Air Raid CAI and as told by the Ford dealership these engines a very sensitive to any modifications with the ECM at factory specs. They advised me to get rid of the oil on the filter as just a minuet dusting on the MAF will cause the ECM to adjust the air to fuel ratio out of calibration. This is usually accompanied by a CEL that will show that the cat and upstream O2 sensors aren't operating within tolerances when in fact its the MAF that has the problem. If your engine hasn't received all the factory ECM updates this will complicate the efficient running of the engine. I know this may not be all of your problems but it could possibly be a start.

 

is your v10 a 4x4? have you checked if the front hubs are disengaging? you could be spinning all that extra stuff up front causing low MPG. Also you never mentioned how you drive the truck.

plus one on the maf, BMW is very sensitive to that also (i am a mechanic for them) and cause all sorts of strange things when they go south.

 

I would also check to see if your breaks are not dragging. Check by lifting the truck and turning the wheels.
You have 3 people that suspect the MAF sensor and the K&N.<O</O