sinkrun Posted December 27, 2010 Share Posted December 27, 2010 My 4.0 99 auto XJ seems to be getting really bad gas mileage I thinking its down around 12-14. I tuned it up and no difference any suggestions? Link to comment Share on other sites More sharing options...
webbjeepxj Posted December 27, 2010 Share Posted December 27, 2010 Did the same thing ..... bought an accel tune up kit .... and nothing ...... Change fuel filter, lines attached to fuel filter, and O2 sensor .... I then got 19-22 mpgs :clapping: Link to comment Share on other sites More sharing options...
xjrev10 Posted December 28, 2010 Share Posted December 28, 2010 must be a bone stocker. my 2000 xj with stock gears, 31s, all the plastic junk off, when its 30 above or less, i get 10mpg. Yes 20mpg seems to be the common mpg reading for a stock L6 XJ. Link to comment Share on other sites More sharing options...
Burls Posted December 28, 2010 Share Posted December 28, 2010 My money's on the o2 sensor. Change it and i bet your mileage will be up to the 18-20 range Link to comment Share on other sites More sharing options...
boman40 Posted December 28, 2010 Share Posted December 28, 2010 O2 sensor, fuel filter, and run fuel cleaner in it. Try and find some with out alcohol in it. I get better mileage running premium. Link to comment Share on other sites More sharing options...
xjrev10 Posted December 28, 2010 Share Posted December 28, 2010 O2 sensor, fuel filter, and run fuel cleaner in it.Try and find some with out alcohol in it. I get better mileage running premium. But what you pay extra for the gas you are not saving anything :dunno: Link to comment Share on other sites More sharing options...
JeepcoMJ Posted December 28, 2010 Share Posted December 28, 2010 so....when is someone going to chime in that you literally can't change the fuel filter on one of these without dropping the tank? oh...right...that'd be this guy. I'm just saying...the filter on a '97+ xj is in-tank and not replaceable...have to replace the complete sending unit to get it... Link to comment Share on other sites More sharing options...
sinkrun Posted December 28, 2010 Author Share Posted December 28, 2010 Looks like this has 2 (?) should I replace both or could I try one first and if yes which one? Link to comment Share on other sites More sharing options...
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