1997 Jeep Grand Cheerokee

I have a 1997 jeep Cheerokee. Everytime my jeep stops at a light it will stall. Also, my enginge light is on all the time. Now after a driving for like an hour It will not stall but, if the jeep sit for a while it will start to stall again. I had the crank position sensor replace and that is when all my problems began. Can you tell me what the problem might be.

Thanks :)