I have a tps code (faulty signal I believe) and the car does have a rough idle but can a tps slowly get worse or do they just quit working? I've read that they can get out of adjustment some how..but how? I just ordered an oem tps so if that doesn't fix the problem I'm leaning towards the fpr... Car seems to be running rich and can smell gas when getting out of the car and mpg is averaged at 20.

 

There is no adjustment on the 850 TPS. The TPS is just an electrical device that produces a variable resistance based on throttle blade angle, it can go bad in any fashion.

 

Think of the TPS as an older dimmer switch like on the mid 70-80's cars.
You could turn it to adjust the dash lights and sometimes you hit spots where they go off instead of adjusting then come back on. Same basic design.