2000 grand prix gt engine cuts out

the engine cuts out while driving at all speed and all temps but it only really stalls if its idle and is acting up... it dont do it all the time and seems to run fine besides that and i think gas mileage is going down also from 22-23 to 17-18mpg....any ideas where to start? i know it could be one of many things so is there any history of this with anyone eles...please help and thank you all i love this site.......it drops in rpm's like it has died but no dash lights come on and then takes off again...it happens at idle,crusing, and acceling...and it dont do it all the time sometimes i make the trip to work and home with little or no problem at all then i leave again and it acts up bad...the only recent work done is the blower motor and this problem started one week exactly after i replaced that..tranny was done a year ago. and no check engine light latley...it was on last winter and the code was something about it not getting to temp its starting to get cold in ohio again so i plan on doing thermostat this weekend i changed temp sending censor about a year ago also

Welcome to AF.

Your description is quite vague and hard to understand. Can you be more specific as to what your car is doing. Also, is the check engine light on? Have you recently performed any work to the car? Does the cutting out happen mostly at idle as you slow down from speed or at cruising speed when attempting to accelerate?