02 fx4 horrible gas mileage
 

i know i am not the only one with this problem, but i bought my truck 2 years ago and used to be able to get about 16 mpg in the city. now i am lucky to get 11 mpg. i have a k&n cold air intake, and flowmaster dual exhaust. i do not have near the power i used to have when i first bought the truck. it has 91,000 miles on it. any ideas on how to improve the mpg and horsepower issues without installing a programmer? thank you!!!

Have you replaced the spark plugs yet?

I'm having the same mileage issue with my '02 5.4L w/ 112,000 miles on it, except mine started out worse. I bought mine about a year ago and the best it got me around town was 11-13 mpg around town and 15 mpg highway. Now it's only getting 9 mpg around town. I will admit that I drive with a heavy foot but I can't believe that that's the only reason I'm not even getting 10 mpg. No idea when/if the plugs were changed, would that be a good place to start? Any other suggestions? Thanks.

At 100k I replaced my plugs and coils. Cleaned my throttle body and replaced the IAC cleaned my mass air flow sensor. I also serviced the transmission and the axles. My truck run like new. They need maintenance.. Did all my brakes to.

One I have seen suggested by the tuners is to replace the O2 sensors at 60K. While these are "life time" parts ( don't replace until they break ), over time they can start to change the output curve on them.

While on the TPS >80% this means nothing ( and TPS > 80% means crap mpg ), the bulk of city driving might be done in the TPS <= 80% range, which is closed loop. The feedback from the O2 sensors will adjust the pulse width of the injectors.

Which brings around a question, what have you done for the injectors ?

The big item I don't see any mention of is the fuel filter, these are good for ~ 30K miles, depending on where you buy fuel at.

The brand of fuel you purchase can also make a difference. Fuel like Sunoco and Valero has more BTU per gallon then the other fuel brands. If one switched to a lower cost fuel when it was over 4.00 / gal, you might have fouled a fuel filter, and clogged injectors, and noticed a drop in mpg. No brand stations bottom pull the fuel that the brand names don't want in their pumps. If the storage tank is not a movable top, condensation can build up, and add water to the fuel, resulting in lower BTU content per gallon.

Tire inflation also makes a difference, every 10 * F is a 1 PSI change in the cold inflation value. If one ignores their tires, as they don't normally loose air, and the temp dropped 50 * F, 5 PSI is gone out of the tire. This is a median value, I don't recall if altitude has an impact on this or not.

As jethat pointed out, basic maintenance is a big part of keeping the truck running like it did day 1.

Your heavy foot can bring down your mpg a TON... How often do you get stuck in traffic and then feel the need to keep on the bumper of the car in front of you to keep others from 'cutting in'?? That's gonna waste a TON a gas... You have to keep hitting the gas, then the brake... Think of every time you hit the brake as WASTED GAS... Especially after the fact, you just had your foot on the gas to keep that 3' space... ;)

You'd really be surprised how much MPG you can gain by keeping to 60 mph on the hwy and not hitting that 'go' pedal as much to keep others from 'cutting in'...

It's all FREE, but you have to drive like GRAMPA!! Ha, ha!! Your choice??

Mitch

I did my o2's and I do the fuel filter every year.. Fuel filter =$15..

I REPLACED my fuel filter, air filter, PCV Assembly, cleaned MAF, new MC plugs and COP'S and it improved my truck performance by alot, and my MPG's went up. I live in a very rural area with alot of stop and go and alot of hills. Before winter hit, I was getting 13.5 MPG average and a couple of trips to my son's place in Albany (300 miles round trip) I was getting 17 MPG driving 67 mph on the NYS Thruway. I had the Dealer do a tranny flush and I also replaced "ALL" fluids in the truck. I plan on keeping it for awhile so it is well worth the expense.
Right now with "winter-mix" petro, and needing the 4x4 alot lately, I won't even check what I am getting for MPG. I will guess, maybe 10 MPG. With gas being $1.78 a gallon locally, no worries. ;)

Like Jethat, I will be cleaning the TB and IAC 1st thing this Spring. Can't wait. :banana:

Welcome to high ethanol content gasoline and screwy regional and seasonal fuel blends.

Peoria, IL? Go try some BP gas and see what you get for mileage. When I lived in IL, I got measurably better mileage consistently on that than any other brand. Down here in MO, my mileage blows on anything because it's all state mandated E10.