Car stalls

My car will periodically stall when I come to a stop or have my foot off the gas, even when driving. It will be fine for a few days, then just cut off. Radio and lights stay on and sometimes it will sound like it is shutting down( idiot lights come on)so I stick it in neutral and turn it on and its already on. I had it into the shop and they put a new idler pulley on for $160.00.