99 GASER W 5.4 TRITON GETTING 10MPG ON HIGHWAY? - Diesel Forum

BETCHER78 · 02-03-2007, 06:07 PM

Checking to see what most of you are getting for highway driving with the 5.4 this is in a 1.5 ton 4x4 mind you.. saving up for a 250sd Di. as soon as i get my 05 stanger paid off in another year.. anywho. i have around 201K on it now.. very well mantained truck. just put 2 new heads on it because #3 poped the plug out @ 197K. this is the only major repair to the truck from purchase date. all matainence performed like clock work. tranny, dif's ext all fluids changed.
i have cooper stt2 tires on it. used to have goodyear mtr both 285's.
i now have had the topper off for about 6mos. mostly drive the car to adn from work 35 each way, but no salt on the car.. so driving the truck. rpm's are what they always have been around 2K at 75mph.
no trouble codes. not sure if it could just be the cold. only let the truck warm up for 2 mins at most before i head out.
anyone think it could be mass air, tem sens, oxgn sens? going out..
any ideas are greatly appreciated.
went from getting 310-315 miles out of 21gal to getting 200-220 out of 21/21 gals..
Brant b.,

westport · 02-14-2007, 04:05 PM

Brant,
Did you ever get it figured out? Don't know if it will help but I had a 99 ford windstar that started getting really poor mileage. Turned out the intake gaskets were leaking and the EGR ports were plugged up. I don't know if the 5.4's have the same issues or not.
good luck

scott

rogerwl4 · 02-25-2007, 04:54 PM

i had a 5.4 in an F-250 it too was a 99. I got 10mpg city and 14mpg highway. hope this helps

kevinmathis · 02-26-2007, 11:13 PM

put the topper back on and run some fuel system cleaner

BETCHER78 · 02-28-2007, 09:45 PM

Thanks for all of the replys.. the intake gasket set is new as i had 2 new complete ready to run heads installed at 197K miles.. It got about 4 points better when it warmed up .. i only let it warm up about 1-1.5 mins at the most before i goto work.. oh well.. i did have coil pack #8 go out . so i just replaced coil pk adn plug.. still about the same mileage.. i will see if it improves next tank. i will check the egr valve.. i do have a new egr controller and a new valve as of 172k.. maybe something plugged it up.. not sure.. no service engine light either.. soon it will be warm enough to drive the stang.. .. thanks again guys..

bb

BBBxcursion · 03-01-2007, 02:24 AM

Windstars are a completely different problem. For the V10, maybe clean the MAF. The best way to find out what's wrong is with a good scanner. Watch fuel trims, graph MAF, O2 switching, DPFE, etc, etc. Clogged cats can cause a nice dent in MPG also

BETCHER78 · 03-01-2007, 11:13 AM

cats are a question that i have raised with several ford techs ( master techs ) all in all i have never had any exhaust issues in that part. i removed the muffler after i hit a re-tread on teh interstate, straight pipe from the cat back.. actually gained about 1mpg or so on average.. had a manifold leak around 197 but thats when the #3 plug almost went through the hood. so those were all set up with new gaskets and studs..
the cats have never been replaced they now have 203K on them. i would think they should be replaced..

any other opinions on this..?

thanks all.
bb

YT90SC · 03-02-2007, 01:48 AM

you SURE that the CAM timing is right? you said you had heads put on.. it is all too easy to get a cam off a tooth. I have also seen the right and left cams timed 180 out to each other. Runs ok in both cases, but just a tad rough and mileage sucks.