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Where the gas mileage go?

balor

NAXJA Forum User
Location
Benton, AR
My 99 XJ Sport is getting about 15-16 miles to the gallon. I was running 19-20 miles a gallon. Changed plugs, wires, cps, and rotor all within the past two months.
Are there two o2 sensors on the v6 4.0 liter? And which one is the moist important to change?
 
balor said:
My 99 XJ Sport is getting about 15-16 miles to the gallon. I was running 19-20 miles a gallon. Changed plugs, wires, cps, and rotor all within the past two months.
Are there two o2 sensors on the v6 4.0 liter? And which one is the moist important to change?

Wow...

It's an I6 (inline six), not a v-motor.

You need to do some research. This forum is a great place to find all your info. Just search around and you will find more than enough. If not, then post up again, indicating that you couldn't find what you were looking for.

Are you lifted, running larger tires? How high, what kind? We need more info if we're going to help...

I'm not sure if there are any o2 sensors on the motor itself; my single sensor that I know of is on my catalytic converter.
 
I'm going to presume that you have over 100K on your '99. The O2 sensors would be a good bet to look at. Then, I would check the CAT if they didn't solve the problem.

I've recently had a drop from 16-18 to 12-14 MPG and it was attributed to a bad CAT (sounded like a tin can with BB's). I went ahead an replaced both sensors with the CAT and I'm back to normal.
 
My amazing gas mileage just took a dive as well. I went from 350 miles per tank to 250 miles per tank. The first O2 seosor will be my first investment, because the injector cleaner and acetone have stopped working.
 
One thing to think about is the gasoline. In recent months, the government dropped regulations on cleaner-burning fuels after Hurricane Katrina. Up here in Indiana, we switch to the dirtier gas every winter. I pull 19-21 on the clean stuff in the summer, and about 16-17 on the dirty stuff in the winter. Just something to possibly consider before you go changing sensors and cats. My mpg has gone down significantly over the last few weeks also.
 
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