As I was driving home this evening in my 88 745, after the engine was fully warmed up, I noticed the tach needle was jumping around, something it has never done before. On closer examination, I determined it was jumping up 500 to 1000 RPM above the actual reading, but never dropping below. The jumping had no particular rhythm to it, but seemed to be happening variously from twice a second to once every two seconds. The car also seemed to be running a little rough and down on power. Very occasionally it would miss. This went on for several miles. Suddenly it lost power and stalled. As I was coasting, looking for a place to pull over, I tried cranking it to see what would happen. Much to my surprise, it started right back up and ran normally. The tach needle was steady. It ran fine the rest of the way home. I went through the distributor less than a year ago. The three little wires to the hall effect sensor were good then, and I replaced the plastic block connector they fit into. Any suggestions as to what to investigate first would be much appreciated.