I have 2001 blazer 4wd. When I'm driving and I come to a stop sign or red light, my truck cuts off. It starts when I'm slowing down and pressing the brakes. As the truck is getting ready to stop, it starts to shake and it cuts off. I than have to put it back and park. The truck starts back up right after that. I have changed the dist cap and rottor botton. Any suggestions on what's wrong?