Good day all,
My question is this...My 99 F-250 LD 5.4L needs tuned. It is quite obvious that Motorcraft plugs are the way to go. With that said. Will changing the distributor,coil, and wires help with with a daily driver? I guess I'm trying to squeeze a few more MPG and perhaps a few ponies when I need them. I'm currently running a stock air box (with a K&N) and factory exhaust. Would it be money better spent on these mod's (air and exhaust) to acheive what I want? Then that opens the questions as to recomendations for those items? I dont want the truck to be loud, but maybe growl when I'm leaning on it . I do a lot of open road driving and don't want to loose what of my sanity I have left to cab noise from a loud exhaust.

Thanks in advance.
Ithaca

 

Well to start with, your 5.4l does not have a distributor or spark plug wires. It has Coil On Plug system with a coil connected directly to each spark plug. I went with a flowmaster muffler and dual tail pipes it sound and looks great. Not sure if it helps much with performance though

 

Plugs, PCV valve, fuel filter, air filter would be a good place to start.

 

Which Flow Master exhaust did you use. Any recomendations for fuel filter, PCV or is stock always best??

 

Fuel filter brand doesn't matter, but stay with Motorcraft for the PCV. It is very unlikely that any modification you can do will increase mileage a worthwhile amount. Ford has been trying for years! Just drive smooth.

 

with my mods below, i was able to only squeeze 1-3 MPG...and believe it or not, running the 93 octane gets me better mileage...AGAIN, i am running the Hypertech Power Programmer, otherwise, the increased octane is a waste.

 

I have never understood the number of people in these forums that purchase a full size truck with V-8 motor & complain about gas mileage. My First Ford was a '64 Long bed that had a Big Block dropped in it & I was Happy then to get a Whooping 10 MPG!!!

Second Ford was an E-150 with 302 it never got above 12MPG even after many hours of fix or repair not daily but it was a used van that was not well cared for.

Third was '91 F150 EXT CAB with 302 15 MPG I was elated! Best MPG I ever got in a V-8. & That Brick body as soon as you lift your foot off the gas on I-40 it slows immediately!

My Fourth is the '03 Screw with the 5.4L, best mileage I have gotten out of it has been 15.67 after Rotation & balance Align & Tranny fluid / filter change. I normally average 14.2 ( my lowest, hauling a load in bed over Jellico Mountain from KY to TN) to 15. Let me tell you I was surprised to see the 14.2 Traffic was bad & We did a LOT of Sitting & Slow moving as snow fell on us & people wrecked every 1/2 mile or so.

If you want gas mileage you do not purchase a LARGE Heavy Vehicle with a BIG MOTOR! But if you do the bigger the motor in the tank the better the mileage! My First job was as a Delivery driver. The man that trained me for the route was an avid Stock car racer. He told me to Always drive like their was an egg under my foot on top of the gas pedal. you get best mileage with the least effort. Coast as much as possible you know a heavy vehicle once rolling does not need a push to keep going.

For Mileage try a VW Diesel Auto my Dad averages 52 MPG in his!