I have a 94 xj 5 in lift 31 x10,5 tires roof rack thats about all ive been averaging out my fuel economy and im getting about 120 miles to a full tank... i have a new fuel filter new air filter i ran fuel system cleaner and seafoam and its not getting better

 

I'd check for codes if you can. Then reset you ecu. See what happens your next few tanks. Could be bad o2. Or a number of other things.

Sent from my DROID INCREDIBLE using Cherokee Forum

 

i scanned it and it isnt throwing any codes wouldnt an o2 sensor throw a code?

 

Whats the tank size? i know on my swb comanche its 18.5 gal but idk what a xj tank holds

Brandon

 

When was the last time you did a tune up... a bad o2 sensor will not always throw a code... how many miles do you have one yours>?

 

The o2s may still work just not working right. It will read wrong but still technically will work. Until it stops working it won't throw a code. You only have one and I believe its only like $60 bucks or so. Give or take a few bucks. More for a very good quality one tho. But that's what I would do.

Sent from my DROID INCREDIBLE using Cherokee Forum

 

And a new fuel filter and air filter is nice. But a full tune up would be best. Plugs, wires, cap, and rotor. That's the basic tune up. Won't cost you an arm and a leg. I did mine for like $80 bucks. All good parts too. In fact Accel makes a kit with all that and its priced very reasonably. I didn't want to wait for it to come in so I didn't get it. But I read on here people used it and it worked well.

Sent from my DROID INCREDIBLE using Cherokee Forum

 

Ditto to much of what's been said already. Get a good quality O2 sensor and replace the one on there (most likely it's never been replaced if you're not the original owner). You may not be getting a code, but that only means it's functioning enough to not trip a code. Kyledye25 is also right in that a tune up is probably in order. Just doing the filters and running SeaFoam through everything won't take care of all the issues. I definitely recommend the ACCEL kit. It's around $70 and gives you everything you need to do a basic tune up for your ignition system. The parts store will probably have to order it, just so you have a heads up that it'll take a day or two before you can actually do the work.

 

How many Gallons of gas are we talking about over how many miles? Maybe your gage is bad and you are only using 1/2 a tank. That said Tune-up is first step, make sure there are NO intake, fuel or exhaust leaks. What is condition of transmission. O2 sensors and bad cat can cause bad MPG. 5" lift and a Roof rack alone can cost 2-5 MPG.

 

dang only 120 miles to a tank, I thought the smallest tank they put in XJ's were 16 gal which means you are getting 8mpg.

 

have you had your speedo calibrated for those 31's cause that will throw EVERYTHING OFF and you have probaly been speeding

 

to answer all questions there are new plugs and wires and there is well over 200k on it the t case was rebuilt for 31s as well and my cherokee has a 20 gal tank giving me about 6mpg at my best guess.. could it possibly be a map sensor? ill do the o2 today if i can

 

are you down on power at all? your CAT could be starting to break up and clog up

 

I'd be looking for leaks also......

 

my cat does rattle quite a bit but it alays has so im not sure if im loosing power or not its been the same sence i bought it as fas as i know... i was thinking of just cutting it out....is that even somthing i could do or would it throw the back pressure way off? im running a flowmaster super 10 and i dont believe i have any leaks