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  #1  
Old November 2nd, 2005, 09:53
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balor balor is offline
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Where the gas mileage go?

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?
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Old November 2nd, 2005, 09:59
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Starscream Starscream is offline
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Re: Where the gas mileage go?

Quote:
Originally Posted by balor
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.
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Old November 2nd, 2005, 10:05
aardvark4x4 aardvark4x4 is offline
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Re: Where the gas mileage go?

There are 2 oxygen sensors. The upstream one in the downpipe is used for fuel control, the downstream one in the cat is just to monitor cat performance.
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Old November 2nd, 2005, 11:25
rstarch345 rstarch345 is offline
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Re: Where the gas mileage go?

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.
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Old November 2nd, 2005, 16:49
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zfinger zfinger is offline
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Re: Where the gas mileage go?

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.
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Old November 2nd, 2005, 17:07
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JeepMaz JeepMaz is offline
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Re: Where the gas mileage go?

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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