Countour stalls?

im having problems with my 98 countour. When i slow down or come to a stop the car stops and i have to put it into park and restart the car. I have already replaced the battery, thermostat. my car is in need of an oil change but i dont think thats what is making it stall. i also need an O2 sensor but that is also not making it stall.

does anyone have an idea on what it could be?

pull the plugs and check the gap, replace plugs if they are bad, replace wires and replace coil pack (shouldnt be more than 70$ for everything). My car idled very rough and stalled a couple of times, it also didn't have any power either. It was the coil pack.

thanks ill look into that, i know its not the spark plugs because i replaced those as well due to the oil leak i had which i also fixed with a gasket.

ill look into te coil pack, thanks a lot!