Phil99

Damn right it's too cold. Where abouts are you located in Minnesota that's where I am.

xjrev10

Im up in Virginia. We have been having 25 below nights since last week. Guess it is supposed to warm up later in the week. Where you from?

brucinus

I have a 2000 6 cyl cherokee. Since november I have been tracking my milage. Here are the results:
miles gal mpg
1/27/09 106.0 15.830 $1.58 6.7

1/06/09 134.0 15.340 $1.54 8.7

12/12/08 121.5 13.520 $1.48 9.0

11/24/08 151.6 11.118 $1.79 13.6

11/03/08 214.3 13.050 $2.30 16.4

I had a complete tune up after the 1/06 fill up. I guess I should ask my mechanic about the MAP and O2 sensors. Could it be some thing else?

caged

jeeps use more fuel during winter months. due to both the winter gas mix and jeep mechanical issues. if you live in snow country, of course...

during a cold start, the jeep will use more fuel until it warms up to operating temps.

also, if you have your heat on defrost, that will use the AC compressor thus using more fuel too. the same as if you have it on max air.

add that to idling your jeep to warm it up before you go out...

this is why i'm only getting about 250 - 300km to a tank in my tj. 4L 5spd on 33's with 3.73 gears.

Phil99

I'm live in the borring city of city of st Paul for a guy with a jeep. Dang man your up in the freezer of the state.

brucinus

My wife does let it warm up every morning before going to work. I'll check if she leaves the defroster on.

I was wondering if the odometer was hosed.

I had a "74" Chrysler New Yorker that got better milage.

mycherokee1989

XJRev10, whats this universal o2 sensor? let me know when you put it in, and if it changed much.

lifted93xj

I still get bad gas mileage and ive tried everything

Thacu_Peaman

I'm back with an update as promised. Replaced the "upstream" O2 sensor a week ago. Averaged 13.75 MPG on the last full tank of gas since the install. I didn't use 4wd, and I did my best to conserve gas. I also checked my odometer against highway mile markers to make sure that my slightly oversized tires weren't screwing w/ the numbers. Odometer registers 3% low, or 97 mi for every 100 traveled, so this isn't much of a factor.

I could only find one O2 sensor on my '98 4.0L, the one right on the manifold, and there's only one mentioned in the Hanes repair manual too. I don't have my original owners manual.

So in summary, I started out w/ about 12 MPG and by doing: complete tune up, new O2 sensor, and ran a bottle of SeaFoam through w/ gas it improved to 13.75 MPG.

A friend of mine in NC says she gets 16-17 city and 22 hwy consistantly, averaging 300-350 mi/tank. This leads me to believe that there's still something wrong w/ mine... unless she's got a 4-banger and just doesn't know it. Anyway, I'll gladly listen to any other suggestions you guys might have. Thanks

aa120nsays

i need to no what to fix. ive heard that it could be 02 senser but i need to no befor buy somthing i dont need

offroadnut36

Cracked exhaust manifold would throw the o2 sensor wayy off. for instance your jeep could be running fine but the o2 sensor would get a bad reading cause the amount gases going into it are false, causing the pcm to put more fuel into the mix.

donnmcc

Did you disconnect the battery?Every time I do something on mine I disconnect the battery to clear the ecm.Then when I hook it back up and start it ,supposedly it relearns.I read it somewhere and have just always done it.Can't hurt.

danimal

Some people will say that an O2 sensor should be part of a tuneup just like plugs, dizzy cap and rotor, wires etc.

On the other hand I've never replaced one on any of the vehicles (quite a few) I've owned.

anomoli

Here is a link to a fuel economy site, that shows your ACTUAL mileage per gallon, not the EPA mileage, which is higher.

Example, My '97 with 4.0 auto and 4WD shows 13 city, 18 hiway, with a combined average of 15mpg, (hiway/city).....ouch.

Click on this link: http://www.fueleconomy.gov/

on upper left, find a car, follow the links, if you click on your model, you will get your combined and other info. This was the site that the dealers used for cash for clunkers.

Obsidian8

Hi I see that this topic hasnt been touched in years but I was wondering if folks ever got the mpg issue fixed and if so what was it? I recently got a jeep(1998xj 4.0) and I'm avg 200mpgs per tank last things I need to check are: o2sensor(pre-cat), map, and maybe replace CAT...