01 XJ automatic. 3.55's and 33" all terrains on lightweight alloys. Should be getting at least 14 mpg (based on my last 3 similarly equiped Jeeps). No cel, no smoke, runs properly at 210 degrees. Any thoughts other than o2 sensors? I have 4 of them and dont have $300 to replace em.

 

Gears is what increased mine 3.55's 7-9mpg 4.56's 13-16mpg 33x12:50 M/T's steel wheels, 4 1/2" lift lot of extras for wind drag and extra weight.

 

Ever replace the speedo gear to compensate for the larger tires? If not, your calculations will be off....

 

Sure did, checked with gps and speedo is dead on.

 

Gears would help, but like I said my other similarly equipped jeeps got better so whats going on with this one?

 

Know very little about yours but it is one of the newest and with the 4 02 sensors but mine was that way as soon as I upgraded mine.

When I was shopping for an XJ I capped the year at a 99 because of some of the issues of the 00/10 models. Are you getting codes from all of them or do you know for sure.

I purchased an "Ultra Gauge" online and have been very happy with it, in fact ordered another one for my GC. You might have a look at them to see if they might be of any help to you, they go way beyond any scanners I have ever owned.

 

No codes at all, thats why I looking for ideas. Ive had the jeep for a few years and havent changed the o2 sensors and I know they can get lazy before they set codes so I was just shooting in the dark. I have a 195 tstat and checked the operating temp with a solus pro so thats not the issue. No smoke or anything and she runs good. I suppose a weak coil could be the culprit tho I have no idea how to test the style I have (dizzy less). I was getting 12.5 last summer and it just dropped off to 10 one week and stayed there. No running issues or codes whatsoever, same grade fuel, same gas station.