Volvo: Engine Code 1990 760, fellow owners, random times

Question
After driving the car (760) my son told me that the check engine light came on. I checked for codes and only one came up - 131 and according to the reference it states "Ignition system RPM signal missing on starting".  I have no stall problems at engine starts, but a few days ago the car did stall while being drive.  Does this point to a computer problem? Is there a starting point to begin checking?  

Answer
It sounds like you have a bad ignition control unit, which is used in getting the right timing for the engine spark.  A malfunction here could cause the car to stall out at random times, as the timing fluctuates.  I don't have a 700 series, so I don't know all the in's and out's of your system, but from what I've heard, you should start your search at the voltage signals coming into the coil from your ignition unit.  To get a more definitive grasp of how to tackle this issue, I would suggest going to www.brickboard.com, and posting your question in the 700 series section.  You'll get tons of responses from fellow owners within a few hours.  Good luck!