Chrysler Repair: 2000 Sebring Convertible - Stalling, sebring convertible, serpentine belt

Question
Three weeks, while driving to the shore, my 2000 Sebring Convertible stalled.  I was on a main highway, going about 70 mph and felt the car starting to sputter.  I pulled over to the side of the road and the car completely stalled.  The car restarted; however, about one mile down the road, it did it again.  When the car stalled the first time, I had been driving for a little over one hour.  There had been traffic earlier on, so I was going about 30-45 mph for the first 50 minutes of the trip.  I was able to drive the car home; however, I had to do so by pulling over every 1 to 2 miles as a result of the car stalling.  The car always restarted.  I took the car to my local mechanic, who's business used to be a Chrysler dealership and therefore, he is experienced with Chrysler vehicles.  The scanner gave him no codes.  When you drive the vehicle, it drives perfectly fine until it stalls.  It continues to stall every couple of miles.  Here's the history of the vehicle:  over the past couple of months I have had the following repairs done on this vehicle:  one tie-rod end replaced, lube-oil-filter, serpentine belt replaced, motor mount replaced, fuel filter replaced, rear brakes, front brakes and rotors.  The stalling problem occurred approximately one week after the motor mount was replaced.  The mechanic does not believe that the motor mount being replaced has anything to do with the stalling.  My husband, a former mechanic for 25 years, instructed the mechanic to replace the fuel filter.  The car did not stall out for the first 22 miles and then it went right back to stalling out every mile or two.  When I start the car, I sometimes have to turn the key twice, but then it does start.  While driving, it will hesitate or jerk when it's going to stall out and then sometimes it just comes back alive on it's own, but usually I have to either put the car in neutral and restart it or pull to the side of the ride. Have you heard of other people having this same problem and if so, do you have any idea as to what the problem might be? Thanks, in advance, for your help.

Answer
Hi Kathleen,
Thanks for the excellent history or your problem. I suspect that one of the two ignition sensors necessary for spark is breaking down as it warms up. It then cools slightly, then will sustain the spark for a while, then begin to fail again. While there is a code for each of these sensors, it's threshold for recognition may not have been exceeded yet. Thus no codes.
If you can anticipate the problem so as to have on-board a digital voltmeter you or your husband could measure the voltage pulses between the signal and ground wire of the two sensors at the time of stall. You would also need a socket and ratchet to turn the crank pulley bolt by hand so as to observe the pulsing which would otherwise not be observable if you used the starter motor instead. It should vary between 5V and 0.3V as the crank is turned. If that is not practical or you can't continue to be in this interim condition until one of the codes is set, my inclination would be to change the crank sensor and see if that solves the problem. That sensor is much less expensive than the cam sensor which is part of the distributor on the 2.5L engine, and which appears to require replacing the entire distributor (but I could be wrong about that).
Let me know if you would like the wire color codes to do the voltage test or a brief instruction on how to replace the crank sensor yourself.
The only other sort of failure that can cause stalling without codes is the egr valve sticking open, but that usually produces hard starting/rough idling rather than stalling while going down the highway (when the valve is open anyway).
So those are my suggestions at this point. Best of luck with getting to the bottom of this.