Alright so I have a 1992 XJ that gets around 17 City under NORMAL driving, my 1996 XJ is getting the worst mileage i've ever seen in a cherokee. I filled up on sunday and I drove about 60 miles since then. I'm hitting half a tank already! I've tried everything in my knowledge to increase my MPGs but I still get the same result. I've ran fuel injector cleaner, i've tried feathering the gas, etc. My catalytic converter is rattling and will be replaced in a couple days by the dealership so they reprogrammed my PCM, it hasn't helped at all yet.

My question to you is, is there any direct cause of this problem? Also is there anything I can do to get better fuel economy because I can't afford all this gas that is used just from driving from home to school.

Thanks in advance!

 

I'm with you on this, I fill my tank up almost every week, i only ever drive to school or wherever my girlfriend makes me drive her. And I only put about 40 or 50 miles on and my tank goes down to half also. there is probably nothing that can be done. "It's a Jeep thing"

 

i get 200mi by half tank. then another 100mi then empty. sucks.

 

i relized my guage is jacked up almost quarter little bit less

 

bad mileage can be caused by a multitude of things, I'll start easy, whens the last time it had a tune up? Plugs, wires, dis cap and rotor, have you seafoamed it? Has the upstream o2 ever been changed? (technically it's a maintenance item) fuel filter, have you cleaned the TB (if not and you do so clean the iac at the same time) how is your tire pressure? Are your brakes dragging at all? Do you keep up on air filters? Enough small things make a big issue. Those are just some things to look at.

more in depth things that could help are an intake kit, bored TB, more free flowing exhaust.

 

You need to do a few easy tests, 1 compression test on all cylinders "I bet you have weak rings, your not burning your fuel correctly" and a vacuum test at idle should be 18" of mercury "18" hg or higher" Also a leak down test to see if your valves are burnt.

An engine with bad parts will do this I have a geo that was only getting 25 to 29 mpg found worn rings and 2 burnt valves and replaced them now I'm getting 46 all day long.

 

15-20 mpg is normal for an XJ, if you need 30-something mpg, get a yota tacoma or a yaris... don't know what else to say. Or maybe get a job? just a thought....

 

I think you miss read it he said his old jeep was getting 16 and the current one is getting horrible gas mileage even for the unfuel efficent straight six.

 

I believe you found it.
If the cat is rattling it is plugged/restricting flow.

Once you have replaced the cat and the downstream muffler, give it a tank of gas and recalculate the mileage.

 

I also had bad gas mileage before... But after I've tuned up my jeep and fixed my air intake/exhaust... Everything went fine..

 

what have you changed i get crappy gas mileage also and i dont have a distributor i have coils.

 

Thanks for the insight, all of those suggestions are great! As soon as I'm done with the remaining driver's side rear suspension for my lift, I'll get right to it. Odds are since I was running rich, my plugs are carboned like no other, and as for the wires; they look alright. I have some seafoam which i'm going to run soon and I think I'm also looking at doing a bored throttle body. As for the air intake; I'm so/so about it. I don't know if I'm going to be taking a risk when i go mudding with it... I saw a video of an XJ that hydrolocked because mud got sucked into the intake.. Also, about the free flowing exhaust.... I'm getting a flowmaster in a week or so!!!!!

 

Thanks! I'll definitely be able to see the difference with the new cat on tomorrow!

 

If you have some sea foam, I would do 1/3 of a can into the vacuum line off the break booster to the intake manifold today, don't let it stall while putting in. Turn off the Jeep for 5 or so mins, and start her back up to let the smoke show begin!
Others have different ways of doing the seafoam, some add it straight to crankcase etc. This is just the way I was told to do it, and have successful results on my buddies 94 and 98, and decent results on my 00, but that was only decent because it did not really need it.
After doing the seafoam then replace the cat and plugs.
Even though it says on a can its safe of converters, I would be afraid to run it right after putting a new one on.

 

Do what I do, Get yourself a 4 cylinder beater. For work or school. (I figured, I have saved approx. $1000 to $1200 a year on gas going to work and back) I use my XJ for inclimite weather, Camping, Hunting, Ice fishing, And hauling my dogs around. Probably way I've only put 4,000 miles in last two years. At this rate, By 10 years, I'll be retired. My XJ will have about. 89,000 miles on it. And 29 years old. And I'll have saved $10,000 at current gas prices. More than enough money for any mods, I might want, through out the next 10 years.