Saab: SAAB 1997 900, crankshaft position sensor, probablistic

Question
My car will start and run for about 10 - 20 min. then cut out.  After waiting 20 min. it will restart, but run for only 10 min.  Mechanic replaced ignition, but that did not help.

Answer
Sue:
 It sure sounds like a heat -related component is failing. It takes two things for ignition, spark and fuel. Have your mechanic isolate which of these factors is failing. My probablistic guess would be spark, and since the ignition module was replaced without positive result, one of the sensors feeding it would be suspect such as the crankshaft position sensor (senses engine motion and feeds the spark producing circuitry at precisely the correct instant).
 Additionally, the readouts of the engine control computer ought to be able to shed some light on the culprit.
   Hope this helps.