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Unread 09-01-2010, 06:00 PM   #1
lipripper
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Bad gas mileage after 90 miles offroad use

I have a fairly new to me 01 WJ limited 4.7 quadratrac which gets about 22 miles per gallon on the freeway, completely stock except k&n air filter. On my way out to Searchlight Nevada I was getting about 22-24 miles per gallon on the 15, then drove 90 miles off road. The roads were rocky washes, with lots of vegetation in the middle of the roads. I did bottom out the shocks a few times in the washes. ON the way back home I was getting around 16-17 miles per gallon. Just to confirm I took it out again the next day, and the same terrible gas mileage. From what I've found in my manual, and online, it sounds like the emmision system is not working correctly, but it hasn't thrown any codes yet. I got under the Jeep and removed a bunch of dry vegetation around the gas tank, but couldn't find any disconnected hoses or anything apparently wrong. Cleaned the air filter, same results. Any ideas?

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Unread 09-01-2010, 06:56 PM   #2
WiCkeDuDe
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How are you calculating this? The overhead display uses an average that would be hurt alot by an off road trip. 16 -17 mpg is even a tick high for the 4.7.
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Unread 09-01-2010, 07:03 PM   #3
lipripper
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I am using the overhead display. I've reset it quite a few times and in a few minutes of driving it gives me my new average. I'll do that to check gas mileage on uphile grades, and driving into strong headwinds to compare to flat highways. Stock WJ's are getting 16-17 mpg's? Before this trip I was getting close to 400 miles to a tank. I thought WJ's with 32-33 inch tires were getting 17 mpg and stock much better than that.
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Unread 09-01-2010, 07:09 PM   #4
WiCkeDuDe
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LOL - if your constantly resetting it then the readings are skewed. When you take an average you need a long length of time to take more samples to get an accurate reading. Fill the tank and reset it, then drive until the tank is empty. That will give you a accurate reading. I wish I got 17 with 32s and a 4.7.
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Unread 09-01-2010, 07:18 PM   #5
lipripper
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The display has two mpg options, average and instantaneous fuel economy.
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Unread 09-01-2010, 08:25 PM   #6
straty1987
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overhead recalculates like ever 50 miles i think. but if oyu keep clearing it will give nice numbers

have to do it the old fashion way
take how many miles you drive and divided it by how much gas you put in and will get the answer

i an get 17-18 MPG only hightway on my stock 02 4.7 going 65 MPH for a long time
city i can get 9-12 depending on how and what happens when i drive
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Unread 09-01-2010, 09:53 PM   #7
lipripper
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I like your suggestion, but only have numbers for before the trip back as of now. 153 miles on 6.978 gallons, it comes out to 21.92 miles per gallon at a speed between 70-80 miles per hour. Gearing is 3:73 I believe, the tag on the diff is corroded badly and its hard to make out the numbers correctly. I'll go fill up to confirm my mileage coming back.
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Unread 09-01-2010, 10:28 PM   #8
lipripper
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Just filled up......164 miles on 9.988 gallons..works out to 16.41 mpg.......somethings wrong in the system, any ideas?
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Unread 09-01-2010, 10:33 PM   #9
straty1987
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Quote:
Originally Posted by lipripper View Post
Just filled up......164 miles on 9.988 gallons..works out to 16.41 mpg.......somethings wrong in the system, any ideas?
this sounds right for a 4.7.

what do you mean by system?
the jeep
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Unread 09-02-2010, 12:23 AM   #10
myjeeplovesmud
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i like to reset mine on big hills, throw it in neutral, and see 99.9 MPG on the reading... it makes me feel better about myself
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Unread 09-02-2010, 01:31 AM   #11
lipripper
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Quote:
Originally Posted by myjeeplovesmud View Post
i like to reset mine on big hills, throw it in neutral, and see 99.9 MPG on the reading... it makes me feel better about myself
too funny:
no reasonable explanation for the loss in mileage then. By system, I mean emission systems, evap, cat, 02 sensors, etc.
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Unread 09-02-2010, 02:06 AM   #12
straty1987
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were you driving in the same exact conditions?

do you know which way the air was blowing?

when you off road you will not get great MPG. so if half was highway and half was off road will effect the MPG.

from the factory the best jeep could do was 14/19 and that at ideal driving conditions and most dont see that. but your driving a jeep if you want MPG look at a small car that is not a 2 tone brink on wheels

check to see if you have any codes that is effecting your "system" with a ODBII, most auto stores will do it for free.

can look into doing a full tune up and basic things to keep it running in top shape
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Unread 09-02-2010, 02:52 AM   #13
nlynd1978
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Quote:
Originally Posted by straty1987 View Post
were you driving in the same exact conditions?

do you know which way the air was blowing?

when you off road you will not get great MPG. so if half was highway and half was off road will effect the MPG.

from the factory the best jeep could do was 14/19 and that at ideal driving conditions and most dont see that. but your driving a jeep if you want MPG look at a small car that is not a 2 tone brink on wheels

check to see if you have any codes that is effecting your "system" with a ODBII, most auto stores will do it for free.

can look into doing a full tune up and basic things to keep it running in top shape
You forgot to ask if he was heading up hill or down

On topic, i agree. Constantly resetting your evic will not get you an average. It will just show how bad you drove on that tank of gas. Also,

did you use cruise on the way down, and not on the way back?,
where you heavier due to mud on the way back?
Where your tires properly aired?
Did you bend an axle?
bend a CV?
where your brakes grinding?
Is your alignment off now?
did you make sure your turn signal fluid was full? (had to say it)
ect, ect.


Get your codes checked, give her a tune up like straty said, and pray for that extra 1mpg. my 99 4.7 gets an average of 16.5, little better on the highway due to using cruise but not much. and i have only 83k on it, and im running 245/70/r16's and stock suspension.

Or buy a sissy foreign hybrid and quit whining about driving a real vehicle that sucks gas like a fat kid on cake after fat camp. Cause gas guzzeling V8's are the american way. Screw some sissy gas sipping pansy foreign hybrid. Give me a good ole gas eating, screaming V8 like my grampa had when my pops was but a twinkle in his headlight and a tickle in his crankshaft.
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Unread 09-02-2010, 03:26 AM   #14
Falkon
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You'll always get somewhat better milage traveling from West to East, since you're going with the earth's rotation. Heading toward the West, you need to overcome this force.

Actually, the overhead display is a poor way to figure short distance milage. You are getting some pretty good milage overall.
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Unread 09-02-2010, 05:55 AM   #15
bradbb2005
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really, your complaining about 17 mpg??? I wish...

idk how you were getting that good of mileage in the first place, but you are at normal mpg...thats all i gotta say.

I saw 20 one time on a 1000 mile all highway trip.....i was ecstatic!
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