2000 Plymouth Neon engine problems

In october while driving on the highway with two friends there was a leak in exhuast system. Because everyone in vehicle fell asleep, they ran off the road and hit a 10 foot enbankment. Passenger suffered some serious injuries to hip/head,/rm, and some internal bleeding. All consumers in vehicle were wearing seat belts. Air bags did not deploy. There was no prior warning as to air bags and exhaust system failures. *slc

We have a 2000 plymouth neon and have taken the vehicle in numerous times to dealers in different states for stalling. Happens most often when coming to a stop, it is intermittent and they can never find anything wrong with the vehicle. I am afraid that one day it is going to get one of us killed. It has stalled in the middle of intersections, on on-ramps, and other places as well.