Car (850GLT -95 non-turbo) stalled, checked for ignition and it suddenly started. On the highway it stalled again, I noticed the RPM tacho fell to zero before the engine actually revved down.
The engine would start when cold enough so it seemed heat-related. On the highway I could rip down through gears to get it running again and suddenly we could drive all the way home (10hr drive) without a stutter.
Back home with the Hayne's repair guide I checked the codes from A2, 1-3-1, "no signal from RPM-sensor".

Since I could not find anything wrong with cables, ignition coil or such and only failure code being 1-3-1 I changed the RPM-sensor (about 50$).
All seemed fine for about 30 minutes of driving until it started again, but now the rpm tacho didn't go zero before the engine and no failure code at all.
Hmm... (And also some junkie had stolen my licence plates. Another 15$)

Took the car to the only repairshop around able to take my car right away. He went through the same hell as me and went to his buddy at Volvo who said the camshaft-sensor (160$) sometimes breaks due to the high temperature. He changed it and I have since then driven about 100km so I guess it's OK now.