Open loop? Closed loop? I know I had read about this on the board, but I'm not clear on the definition. I also did a search. My car has a hard time reaching operating temp in the morning since it got cold out. I have a new 180* t-stat installed, and the car barely reaches 170*, even after a 15+ mile drive. Any ideas? I'm thinking it may be the engine temp sensor. Oh, and my gas mileage has sucked for some time now.