rediculous gas mileage

[yjpaul]

Specs : 88 YJ 4.2L(258)

Ok, so i have been calculating my MPG for the last little while with amount filled at the pump and trip odometer readings. I did the calculations for KM to miles, and Litres to Gallons, and got realized that i was averaging 9-11 miles per gallon for city/highway.  What numbers are you all getting? Im not running rich or anything.  Is there anything i can do to help it?

Thanks guys.

~Paul

*Its just $20 every second day is getting to be a joke.

[yjpaul]

and also my emissions matenience light is on. Could this be a faulty O2 sensor? Will it make a difference? because i swapped the carb with that stupid electronic mixture control for the cj carb that was used the year before the electronic stepper motor thing.  What will replacing the o2 sensor do in my case? I just want the light off.  And maybe its making my mileage worse somehow.

Thanks

[yjpaul]

in addition to the specs on the first message, the truck has 31" tires on it and a 3 inch body lift.

~Paul

[CanaMatt]

I had O2 problems, well I had no O2. And gas milage blew. Installed new O2 and I get 60L goes 250 miles in city and 300 in country. Depending on driving habits of course.

[Jaguar]

I just went from an '03 4.0L to an '05 2.4L. On my first tank of gas off the lot, I got 500Km out of her But my gas gague was reading wierd, because the gas light came on half way into the red, so I think I could have gone a little further. She sux on hills though compaired to the 4.0, but looking at gas prices today, I think I can live with it!

Not sure how much it will help since you only went to 31's, but putting new gears inyour diff will help a bit (if you haven't already)

[redbull]

Herea a handy tool for most of us who understand mpg vs. k/L : http://www.eltcalendar.com/stuff/mileage.php

Anyway, I just drove from Moose Jaw yesterday and got 19.5 mpg (8.16K/L) in my 1991 YJ 4.0HO on 31"s. That was with a crosswind and holding an indicated 100km/h. I don't know the true speed since I put on these tires after my GPS was stolen, but I'd guess I'm doing a true 105km/h or so. I notice a huge mileage drop if I try to go much faster than this.

Oh, I'm still on the stock 3.08 gears too, turning about 1500rpm at that speed. Zero power on any kind of hill in 5th,  :x

I've got all brand new ignition on my Jeep too, and I think that helped my mileage. New plugs, wires, cap, rotor and coil cost about 2 tanks of gas. Not sure about what you should expect from your motor though. How careful are you with tire pressures?

[Spinalguy]

i get 14.65 mpg in the city running 37" MTR's. (4.10 gears)

Tom

[Wif]

and also my emissions matenience light is on.  ...
Thanks

Do you mean the maintenance light in the cluster .. it's driven by a timer and can be ignored (most people remove the timer as it is a dealer replaceable item set to go off every 80,000 miles or so). My unit must have been up behind the dash in the middle .. when I had the dash out I found the 3 wires just hanging there ..  :lol:
The 88 didn't have a sophisticated enough computer to fire off a light.

[bae146]

I don't know how much the computer in the yj controls the carb but if you have an O2 sensor and a non computer carb in there you will get the emissions light.  Replacing the o2 sensor will give you nothing, as you cannot govern the mixture with the carb you have.  Basicly your computer is useless.  You must now try to tune your carb manually.  You also should check your ignition timing.  On my scrambler I set the ignition advance to 16 degrees btc, and swapped in a ford large distributor with the bigger coil.  I averaged 20 mpg on the hightway with 3.73's and 33X10.5 bfg at's.  Make sure your air filter is clean, spark plugs and wires are good.  Synthetic fluids are good for reducing friction, and increase fuel mileage.  Check your tire pressure and ensure it is appropriate for you vehicle weight and tire size.

[Sludgefactory]

http://www.jeeptech.com/wiki/index.php/Engine/Carter :idea:

[Dragonmaster]

Try this link for your mileage  http://www.royalbank.com/cgi-bin/carloan/gas.pl

It spits out all the different types of mileage figures really easy.

[89YJGUY]

My 89 YJ w/33's and 4.10's was sucking pretty bad as far as gas mileage goes.  In early July I topped off the tank in Calgary and then drove back to Lethbridge.  The gauge was reading so low I filled up in Coalhurst (a small town about 10 km short of my destination.

For the last half year I have been experiencing intermitting stalling and idling problems.  A mechanic talked me into buying a new carb (after he adjusted it 2 times with no success).  I also replaced the plugs, ignition coil, rotor and distributor cap.

Anyway, to  make a long story short - after the YJ died and could not be started I finally managed to track down the culprit - it was the ignition control module (located under the radiator overflow bottle).

After it was replaced my fuel economy went way up (can't give you exact #'s a my kids keep resetting the trip odometer to zero on me.

I suspect that perhaps I wasn't getting the proper spark and as a result, the vehicle was using more gas?

Note: Some parts stores (I went to Auto Value) can test your ignition control mod to see if there is a problem.

Other than that it could be the usual culprits:
-dirty air filter
-bad plug(s)
-poor driving habits
-tire pressure


Hope this helps.

[Rubiconman]

I believe you guys are having some serious issues..I have been getting 60-65 MPG lately...ar..ar..ar

[Milan]

13.5l/100km or 17.42mpg. I don't think anybody uses km/l, though it is kind of usefull to know how far the tank will take you.

This is highway only. City driving is worse. 35" Krawlers and about 5" of lift total. Heavy vehicle too - over 4900lbs.

Stock or nearly stock I was getting 10.5L/100km or 22.4mpg.

98TJ w/ 4.0L

[Iron James]

I get around 16.3L/100km according to my in dash computer thing in my 93 cherokee stock. I think its crap but we ve got to live with it.