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Savvy/Currie Aluminum Control ArmsRockridge 4WD IS Taking Zone Offroad Suspension Lift Kits ZONE 4.25" combo lift for TJ available at Rockridge4w

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Unread 12-15-2012, 10:39 PM   #1
DerMeister
Registered User
2000 XJ Cherokee 
 
Join Date: Apr 2010
Location: MI
Posts: 768
Need some help, out of ideas.

I'll try to keep it short. My XJ has been getting 13-14mpg on average for a while now and will do just under 16mpg at its best on the highway.

I used to get 17-18mpg on average. I used to get 20-21mpg on the highway.

2000 XJ
4.0L
AW4
235's
2" lift

I cannot find out what's wrong with it. Here's whats not wrong:

Tires at 36psi
New plugs and boots this summer
No exhaust leaks
Fan clutch working fine
Battery fine
Grounds fine/replaced
02 sensors were replaced with Bosch ones three years ago, less than 20k
Brakes not dragging, jeep rolls fine
Fuel Injector cleaner used once in a while
Air filter less than a year old
Running 10w-30 oil


I know I'm forgetting things that I've done. The jeep starts and runs just fine and I'm light on the pedal. No codes are being thrown, and I have no idea where to look. 3-4mpg is a lot to be missing.

Please give me your $.02.

No I'm not selling it, and there is no reason it should'nt get the mileage it used to.

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Unread 12-16-2012, 07:47 AM   #2
BigByrd47119
Registered User
1998 XJ Cherokee 
 
Join Date: Oct 2012
Location: Detroit, Michigan
Posts: 153
I assume the lift was installed back when you were getting better mileage? If not...

Sounds like you have it fairly well covered...it does come to temp right (so it doesnt stay in open loop)? Maybe a bad temp sensor (or so some may say, never experienced it myself).

Or...the engine may be getting tired; how many miles?

Paper air filters are usually changed at 3k miles if your using paper?
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Unread 12-16-2012, 08:16 AM   #3
98muddyjeep
rockin lil red wagon
 
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1998 XJ Cherokee 
 
Join Date: Jun 2008
Location: Hatboro PA
Posts: 1,231
Bigger tires will cause a mileage drop,because now the motor has to work harder to turn the bigger wheels.try putting on the stock tires and watch your rpms at certain speeds then put on the bigger tires and you should notice a distance in the rpms at the same speeds.
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Unread 12-16-2012, 10:27 PM   #4
DerMeister
Registered User
2000 XJ Cherokee 
 
Join Date: Apr 2010
Location: MI
Posts: 768
Quote:
Originally Posted by BigByrd47119 View Post
I assume the lift was installed back when you were getting better mileage? If not...

Sounds like you have it fairly well covered...it does come to temp right (so it doesnt stay in open loop)? Maybe a bad temp sensor (or so some may say, never experienced it myself).

Or...the engine may be getting tired; how many miles?

Paper air filters are usually changed at 3k miles if your using paper?

I got the bad mileage before and after the lift. Didn't lose any when it went up 2".

It comes to temp fine, and I remember that I also replaced the coolant temp sensor when I was doing cooling system maintinance .

Engine runs fine, burns no oil, loses no coolant and only has 117k on it. I am using a paper air filter and it was replaced within the last 3k. It isn't very dusty around here and it still looks new.

The tires are only 235's, one size above stock. I know the odometer is off slightly and I adjust for that when figuring mileage. Also, I had the 235's on it before I started to get ****ty mileage too.
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Unread 12-17-2012, 09:44 AM   #5
BigByrd47119
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1998 XJ Cherokee 
 
Join Date: Oct 2012
Location: Detroit, Michigan
Posts: 153
Quote:
Originally Posted by DerMeister View Post
I got the bad mileage before and after the lift. Didn't lose any when it went up 2".

It comes to temp fine, and I remember that I also replaced the coolant temp sensor when I was doing cooling system maintinance .

Engine runs fine, burns no oil, loses no coolant and only has 117k on it. I am using a paper air filter and it was replaced within the last 3k. It isn't very dusty around here and it still looks new.

The tires are only 235's, one size above stock. I know the odometer is off slightly and I adjust for that when figuring mileage. Also, I had the 235's on it before I started to get ****ty mileage too.
If that be the case, there are only two options that I can think of. Either it has something to do with the winter blend where you live, or your driving habbits must have changed. Thats all I can come up with, but maybe someone else will have a different idea...

Edit:

Have you been running your defroster since the change? That compresser will eat up a few mpg's too.
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Unread 12-17-2012, 05:21 PM   #6
JTM1
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1988 XJ Cherokee 
 
Join Date: Sep 2008
Location: W.Houston, TX
Posts: 254
Winter Blend will cost you some mileage (most regions rolled it out early this year)
Paper Filters are good for 10-15k miles
Change the fluid in your diffs, most people seem to forget it should be changed every 30k miles or every 15k under severe use.
Don't over inflate your tires, its a safety risk.

Check your U-Joints, and Hubs.
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69 CJ5-In peices
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