I've been having an issue with my XJ for a while now. (2000, sport, 4.0L, AW4)
Back in Nov '08 I had the engine replaced with an ATK rebuilt long block & head after the original head cracked near the No.6 cyl. I've put almost exactly 4,000 miles on it since then, and after the engine replacement my MPG dropped from 16-18 down to 12-14. I've replaced both O2 sensors, checked the spark plugs(champions, .035" gap), and even resorted to taking it to my mechanic, who didn't find anything wrong with it. It's not throwing any codes, I haven't changed my driving habits, and the T-stat is good. Any suggestions as to what is wrong with it?
EDIT: i forgot to mention that the spark plugs exhibit some fouling, like they are getting too much fuel.
Back in Nov '08 I had the engine replaced with an ATK rebuilt long block & head after the original head cracked near the No.6 cyl. I've put almost exactly 4,000 miles on it since then, and after the engine replacement my MPG dropped from 16-18 down to 12-14. I've replaced both O2 sensors, checked the spark plugs(champions, .035" gap), and even resorted to taking it to my mechanic, who didn't find anything wrong with it. It's not throwing any codes, I haven't changed my driving habits, and the T-stat is good. Any suggestions as to what is wrong with it?
EDIT: i forgot to mention that the spark plugs exhibit some fouling, like they are getting too much fuel.
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