I bought my TJ 2 1/2 months ago. The mileage has been less than stellar the whole time. I might get between 10-13 mpg, and thats with a GPS tracking the miles and the fuel exploding out of the filler at fill up. ( I already did the complaint for that).
The Jeep is a 2006 Rubicon with an auto. It has a 2" lift and 32" tires.
I have been trying to figure out why the mileage sucks so bad(besides the rolling brick part). When I plug in the scanner and look at the live data, I have to think that the calculated load could be part of it. At idle in the driveway in park, it reads 23-26%. Really 1/4 load just idling? thats with the AC off. If I turn the AC on, it jumps to 33-37%. I was wondering what sensors play a part in the calculated load? Maybe one is clogged or bad?
If you have a scanner with live data, I was wondering if I could get you to post up what your calculated load is idling and with and without the AC?
I consistently got 13-14mpg when I had 33s on stock axles w/ 3.73 gears.
I get 10mpg with 40s and 5.86s.
How many miles does your Jeep have on it?
And as for comparing your ~25% load to Rammer500's ~5% loads at idle in the driveway... remember you're comparing auto to manual. I wouldn't be surprised if the auto is to blame because of the torque converter slipping and the engine needing to apply more throttle to keep the same RPMs.
Also, your 32s with stock 4.10 gears and the 42RLE aren't completely ideal... at 65mph you are only turning around 1900rpms? You're lugging the engine, it really should be 2000-2100rpms to be more close to ideal for a Jeep with oversized tires IMO.
I have 33s and consistently get 15mpg city and 17mpg hwy, I also have the auto, and if the motor lugs I will turn the OD off, if you live in a hilly area I would turn the OD off all the time, unless you regear. At idle in park the transmission should be in neutral so there should be no load coming from the transmission. Considering you mileage the first thing I would look at after fault codes is to replace the clutch on you your clutch fan on the front of the motor. If the clutch has seized that would explain the high loads at idle.
2003 Jeep Wrangler Rubicon
4.0L, 42RLE, Dual Tops, Full Doors, JKS Front Disconnects, Cragar Soft 8 Black Wheels, 33x12.5x15 Goodyear Duratracs, .75" Front Coil Spacers, Bushwacker 6" Flat Fender Flares, Skid Row Steering Box Skid, LubeLockers, Rubicon Locker Mod, OBA, Cobra 19 Ultra III CB, 3' Firestik, Rough Country 2.2 Steering Stabilizer, RC 1.25" BL, RC 1" MML, RC Grab Handles, Fog Lamp Bent Pin Mod, 4" Apline S Series Speakers, Kenwood Excelon 6.5" Speakers, 6.5" JL Audio 6W3V3 Subwoofer (in center console) w/MTX Thunder 202 amp, IPF H4 Headlight Housing, Sliverstar H4 bulbs.