It only happens when you come to a stop? Try this, when you've got it running pretty good, when you come up to a stop sign/light, pull it out of gear (neutral) and leave it there until you're ready to go again. It sounds like your lockup torque converter may be going bad. when the torque converter won't unlock, as you slow down, it slows the engine down as well. When you get going too slow, it'll kill the engine.