I recently replaced my motor on a 89xj,i replaced with same motor and transfered all manifolds and sensors to new block, well im getting 10-11 mpg now and i used to get 16 and thats with the 31"s So 3 days after running new motor this idiot light comes on "service emission" and i thought its just a timer? but my question is can that have anything to do with it? I replaced o2 sensor about 10000 miles ago .. and i can smell it running rich. can it possible be the air intake sensor are have anything to do with coolant temp sensors? i did put a new regulator in cause to old was a leaker,but other that that it runs perfect, has its power back but milage is starting to suck a$$ any ideas? this is the last of the jeep project before i can say its "done". so i can find a new project..