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Old 01-05-2016, 08:19 PM
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Horrible Gas mileage, need suggestions

Ok guys,
Need some serious help.

04 WJ Overland

Mods, 3" IRO lift, Bilstein shocks, New Calipers, New Pads, New Rear braided brake lines, New LF braided brake line.

Fluid changed a couple times in the Diffs.

Have Vari-Lock Diffs.

Superchips Tuned

K&N Intake

Changed External Fuel filter
New Champion Plugs

Changed one O2 sensor a couple years ago, Right front sensor I think


Thats what I can remember so far, lol


Ok Problem == about 10MPG this fill up, between 10-14 calculated over the last several months.

I drive about 2 miles to the Hwy, then 20 to work.

I've tried different driving methods, medium Accel to cruise, Gentle foot accel, ect.

Nothing helps

All bearing checked at wheels/axle/pinion with DeWalt IR thermometer, all temps consistent.

Sooo....Help

-Nick

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  #2  
Old 01-05-2016, 11:07 PM
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Re: Horrible Gas mileage, need suggestions

If you have a scanner with live data, you can check the O2 sensors for working properly. The 1-1 and 2-1 sensors should change voltage more or less rapidly between 0.2 and 0.8V. If one or both is (are) steady, it will be time to change it. I would change those as a pair when needed to change one.
If they seem to work fine, you can have a look at the STFT and LTFT (short term and long term fuel trim) figures. These figures change as well, especially the STFT, but should stay as a single digit figure. As soon as it goes well over + or - 10 for a longer period, then something is wrong.
If you donīt have a scanner, but do have a smart phone, then you can buy a cheap bluetooth or wifi dongle from e-bay and download the free torque app. You can then read and errase faults, but also see many live data, just as a scanner.
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Old 01-06-2016, 09:04 PM
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Re: Horrible Gas mileage, need suggestions





http://img.photobucket.com/albums/v5...ps32fucyz1.jpg

-Nick
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Old 01-06-2016, 09:05 PM
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Re: Horrible Gas mileage, need suggestions

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Old 01-07-2016, 07:06 AM
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Re: Horrible Gas mileage, need suggestions

The STFT and LTFT figures look good. That should rule out the fuel pump, because with a too low fuel pressure, the LTFT figures will go up to the max.
I would check for any exhaust restriction and eventually the compression of each cylinder.
Do you always refuel at the same station? If yes, try a few times some other stations/brands.
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Old 01-07-2016, 08:10 AM
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Re: Horrible Gas mileage, need suggestions

Many different stations locally. Shell to country fair

Also worth noting maybe, I think my rear upper control wishbone is bad, I think the left rail bushing is ripped and I get tail wag as i go from gas to coast. I don't know if this had ever significantly hurt millage, But wanted to state

-Nick
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Old 01-07-2016, 09:31 AM
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Re: Horrible Gas mileage, need suggestions

Quote:
Originally Posted by Sqall12001 View Post
Many different stations locally. Shell to country fair

Also worth noting maybe, I think my rear upper control wishbone is bad, I think the left rail bushing is ripped and I get tail wag as i go from gas to coast. I don't know if this had ever significantly hurt millage, But wanted to state

-Nick
Wonīt expect any difference in mpg due to a bad bushing, only the stability will be affected.
Regarding the live data, do the O2 sensor voltages 1-1 and 2-1 change rapidly?
Any change in checking the exhaust system for restriction?
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Old 01-07-2016, 12:51 PM
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Re: Horrible Gas mileage, need suggestions

Voltages changed as quick as reader would allow

-Nick
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Old 01-07-2016, 02:15 PM
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Re: Horrible Gas mileage, need suggestions

Could your service brakes or parking brake be rubbing slightly?

Wheels out of alignment?

Tires underinflated?

Any transmission slippage?
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Old 01-07-2016, 02:42 PM
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Re: Horrible Gas mileage, need suggestions

Jeep drifts at slow speeds well, parking brake good, New tires good inflation, alignment unknown trans seems fine, about 1900 at 65ish

-Nick
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Old 01-07-2016, 06:35 PM
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Re: Horrible Gas mileage, need suggestions

If the transmission would be slipping to such extend that it would influence the mpg, for sure a fault code for gear ratio would be set. Also if the torque converter clutch would slip, it also will set a fault code for that.
You did check the bearings with a thermometer, but did you check the wheels as well, to be sure no brake is dragging? You did check for eventual fault codes set i presume?
Exhaust back pressure?
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Old 01-07-2016, 07:29 PM
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Re: Horrible Gas mileage, need suggestions

No fault codes, wheels, bearings and brakes, all consistent temps, diffs too
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