poor MPG, sudden MPG gain
Hi, first time poster here, 2004 Dodge GC Anniv. Edit., 80k. Bought it ~4 weeks ago, also because of dec. .mpg.(city), only to find out to be 13.5 to 15 mpg in slightly hilly home-city driving (calculated and overhead display). Noticed soot in exhaust and even a 1/4" soot collar on exhaust, since I bought it. Yesterday filled it up for the ~5-th time (resetting the mpg displ.) later in the evening I looked at the diff. sensor-wires and connectors (temp, MAP, Idle Air Contol, o2) just moving the wires looking for something loose, but found nothing wrong.

Today in the morning the mpg display started climbing from very low up to 18.3 mpg but most of the morning around 17 mpg and changing close to the driving conditions but never below 16.5mpg (all city, hilly) and very stable. This afternoon started the car (was parked all day) and again 13.8 - 15.0 mpg on display, not higher, same driving.

Now, to me it looks like some sensor or wire-connection is causing the computer to misadjust (temp sensor, sending too cold a temp.?) the mixture (soot in/around exhaust) towards rich. Also, IAC/PCV any influence?.The car never displ. a code (key dance 3x). Please let me know your thoughts and ideas! it's driving me nuts. Had to replace the water pump and would like to thank all of you for the info found on this forum, it was very helpful and it is a very helpful forum overall. Thank you, Pietro