My Grand Prix has the 3.8L with 187000 miles. It has started having an issue where if it is on an incline such as going up and overpass or over an elevated railroad crossing it wont shift correctly until after it is on flat ground for a short distance. What it will do is it will downshift to first or second and refuse to shift while going uphill or downhill. Then once it is on level ground you have to let off the throttle and it will fling itself into the next gear. It does it at all speeds and when it does it it acts as if the pedal is being held to the floor when it isnt. Its an odd thing to try and explain. The only code it has on it currently is an evap code. I forget which one it is.
