CheifErik

just this week i calculated my mpg to be 14 mpg. I think this cannot be right. when i drive as efficiently as i can i can only get 16. When i first got my 98 jeep i was geting 17/18. I put on 31' bfg a/t and it stayed steady at 17. and eventually dropped to 16, now 14. I don't think this is right because i know a guy with the same year/model jeep with 31' mud tires and a 3' lift and he gets 18.
Does anybody know any possible reasons i could be geting bad gas mileage?
only thing i can think of is 02 sensor but i dont know much.

Abovetimberline

The things that can effect gas mileage,is anything that has to do with combustion,mechanicaly or electricaly,14 mpg is horrible. 02 sensors can cause it,in your case there is two,one before the cat and one after. Poor compression is another thing that can cause it, restricted exhaust system,transmission slipping if it is an automatic,I assume you do not have the check engine light on?
To be getting 14mpg,i would think you should see some indication of power loss.

RICZR2

Multiple reasons...Change plugs, wires, oil, tire preasure, ect. Sounds like your very aware of your vehicle.....does it seem to run as strong as it used to when the milage was up?

CheifErik

no my check engine light is not on, and yes i have noticed some power loss. I used to be able to do a brake stance no problem. and now it can barely get the tires spinning. but when i am just driving around i feel that its sluggish but nothing too niticeable.

SpitFire

I had a similar issue. No power, couldn't get the tire to spin even in gravel. It ended up being a plugged Cat and Muffler. I replaced both and now the power returned.

This started off slow, reduced gas mileage and such. Then one day I hit a large bump in the road and I guess that jarred whatever loose in the exhaust system and plugged it up real good like.

bspratt

Yeah I am facing the same exact problem with my 99. Its really depressing considering it is my every day driver.

CheifErik

well by December i plan on having new exhaust, cold air intake, tb, and spark plugs so what ever the problem is, it will be fixed sooner or later!!!
thanks for the help

o yea 2 more questions. Is it possible to have bad 02 sensors w/o a check engine light on, and is it possible to check if a 02 sensor is faluty or not w/o replacing it because i dont want to spend unessesary money.

warthog

X2

Great question and good thread, i am having some similar issues, i just tell myself its from the lift to make me feel better. and 40 miles a day is starting to empty my pocket book

94sport

I was running 235/75/15's and I was getting 17/18 MPG. I just installed 245/75/16's which are close to 31's and my speedometer is off by 4 MPH because of the larger tires. When it says I am doing 50 I am really doing 54. This will throw off you odometer as well. Your probably still getting 17/18 or better on the highway. I confirmed this with my GPS which gives me satellite speed & odometer reading. Before I put the new tires my GPS and Speedo were reading the same speed.

89Laredo

My girlfriends 96 is on 235/75/R15s. Left on a 82 mile trip with a full tank of gas, when we got back it took 3.3 Gallons of gas to bring it back up to a full tank. 82/3.3=24.84MPG Going 55MPH on Cruise control.. Get your Oxygen sensors checked out, and do a good tune up..

thaclav

I don't mean to thread hi-jack or anything but is there any way to test O2 sensors? The O2 sensors in my '96 were replaced about 30,000 miles ago and it's getting terrible MPG, 13 city, 15-16 highway, and it's been doing that since I bought it about 15,000 miles ago. I also doubt my exhaust system is plugged because the entire exhaust system is pretty new. I'm not experiencing power loss either, I'm at a loss for what's actually happening. The city milage can be explained because I go on relatively short (5-10 mile) trips with a lot of hills, but the highway milage is terrible.

zjrog

Something else to look at, have you changed your air filter? A clogged filter (have you been wheeling?) can bring mileage and power down...

93XJLI

buy something else if youre concerned about MPG honestly... i average 14 in the jeep. i could get close to 30 in my subaru but i dont drive it that easy.

lex1125

some more good info here:

https://www.cherokeeforum.com/f2/tip...-23736/index2/

cj11

4" lift and 31's 12 to 14 (14 if i am lucky) any tips for boosting it would be great thought about the injector upgrade