Why is my GMC Acadia idling rough after replacing purge valve?

check engine light is on and was on prior to mess up. Also "traction control off" along with "service stabilitrak" and "service airbag." All of these were on prior to mess up though. My son did try to crank vehicle multiple times, with no success. He said it seemed as though the battery was completely dead. Of course that did not stop him from continuing to try and crank. After the purge valve was replaced, I did have a mechanic check it out. He said the traction control light was a concern and he suggested taking it to local dealership. The only issue with that response is all the lights were on prior to breakdown. Mechanic says he doesn't think the plugs are fouled up because vehicle runs too smooth except during idling times. Before the breakdown idle was perfect. After breakdown the vehicle literally begins to roll before acceleration. Also when braking I can feel a slight jerk and then very rough idle after complete stop.