Howdy everyone,
First off I have a 00'XJ Sport with 193,000 some odd miles, and I just wanted to let ya'll know that I've been getting worse mileage day by day, just to give an example, I used 3/8s of a tank doing a 50 mile round trip. I know for a fact that's worse than what I usually get. I've also noticed that whenever I have a constant foot on the pedal my RPMs rev up and down two or three times between 1750 and 2250 RPMS, really weird as if I was trying to rev my engine to look 'cool'. I'm thinking its most likely that my fuel injectors are clogged up but I don't know what the heck it is for sure.
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I would just like to know what might be causing the issue, just worried because its my daily driver..

Thanks!

"The education of a man is never completed until he dies" -Robert E.Lee

2000 XJ Sport//193k//4WD//4-door//Dana-35//Wrangler Bumpers // Gadsden sticker
1997 Dodge 3500//Hemi 5.9L// Dually//Pieceofsh**//Sittin for 3 years and probably will forever

 

First question that must be asked is if the Check Engine light is on?

Next, it sounds like your torque converter is going in and out of lock-up when cruising, which would explain the jumping up and down between the RPM ranges you mentioned. This could be caused by several possibilities such as a failing solenoid in the transmission, or something more mundane like a brake switch that is occasionally sending a false positive to the computer (do you ever notice your rear brake light flickering?). It could also be caused by a throttle position sensor that is failing.