Well as I today do my 2 times a year reprogramming of the pcm, this sounds familiair.
My alero needs to be reprogrammed twice a year, once when outside temperatures drop below zero
and once when its spring and temps rise.
the car (alero 99 2.4) starts to shift rough (hard), idle becoms a bit strange, kickdown hesitates, and shifting starts to get only in the high rev counts
this happens twice a year and only when temps outside shift.
then i pull the battery cables a few minutes, connect again
start and idle until normal operating temp is reached, then 2 minutes at 1200rpm
and next a 5 mile drive and programming is complete
all strange behavior is gone then, nice idle, smooth shifting and kickdown as it should be.
Think it has to do with the MAF sensor and outside temps.
I have the car for about five years now, and this happens every year.
glad it can be solved in 10 mins, and bad it leaves the radio empty.
(got this reset procedure from my Haynes manual, my money saving wonderbook
)