its dumping fuel. if the temp sensor is bad the motor will think its really cold out and go nuts. most gm's don't throw a code for it though. I recomended changin the plugs cuase they are prolly fouled now if its been bad for awhile change the oil too its prolly also fuel fouled.
I called temp sensor mostly cuase I've had the same problem with three cars recently and it was the temp sensor everytime