I have a 96 Grand prix with 140k miles on it and within the last 5k miles i have been experiencing a hesitation problem. My car starts fine in the morning, but if idrive it to work (35 miles) and then turn off the car and wait a minute or so and try to restart my car it feels like it isn't getting enough gas, it hesitaties and will do that for a couple minutes unless I give it some gas. If i put it in gear it is fine, it will just continue to hesitate until i have driven for a few minutes. Now if i slow down for a stop light after restarting the car it will feel like it is about to shut off,i ran the codes and found a P-1870, can someone offer up some advise or possible solutions??