I replaced the MAP sensor ( the old one was so crudded up I was wondering how it could work ) and now the fuel mileage has gone DOWN !! I do not see any sign of leakage around the sensor ( my eight thumbs installation tecnique ) and I am totally cornfused. I'm going to shoot the Airflow sensor with MAF cleaner to see if that may be the problem, but with 82,000 miles on the vehicle, I expected the MAP sensor to be buggered up. Any suggestions on what I am missing ?

Are you sure you reconnected the map sensor harness properly. What mileage are you getting now?

I will check the harness tomorrow, but wouldn't a check engine light come on if it wasn't hooked up correctly? For that matter, how the heck does it run as gooked up as those things get ? Was getting high 23's to low 25's ( hand calculated ) but it is so hard to get an accurate fill with that stupid restrictor in the fillup tube. We got 22.0 on this first tank after the sensor change. Didn't run any bio or cetane improver this last tank. Cleaned the MAF sensor today and filled up with cetane improver in this tank and the overhead has improved by about a mpg. The overhead liar is generally 4 mpg over what the truck acutally gets.

22 doesnt sound that bad. im assuming you dont have a GDE tune or anything of the like? these jeeps are supposed to get between 20-24 anyway i thought so it sounds like youre right in the average.

winter fuel and cooler weather also lower mileage

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2006 Black Jeep Liberty CRD Limited
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The Jeep is stock except for Amsoil and a K&N air filter. I just thought that as gooked up as the old MAP sensor was ( the MAF sensor didn't look all that bad ) that there would be a significant increase in fuel mileage with the new one in. Winter fuel and the cooler weather knocks my Dodge down about 1-1 1/2 mpg . Gonna get the GDE tune this year, diesel fuel prices going the way they are lately. Gotta get tires first.