From what i understand your car is supposed to jump up to like 1500 when cold to heat up the car faster and jump down to like 900 after its hot? Mine idles at like 100 when cold and i have to step on the gas pedal to jump the rpms up until it gets hot then it idles up to about 900 could this be a sensor problem?

 

your car cant idle that low. it needs 250 rpms to send signals to the computer to keep it running. and if it gets below 500 it'll start to stall out. now what is your motor?