stalls

First I'd get 2 things checked, the crank position sensor - actually the shielded cable goes bad on it- it's located behind the cylinder head, mounted right behind the bell housing. Start the car, let it idle and wiggle the cable. If the engine stops, replace the sensor. Volvo calls it a reference sensor. The other thing is the fuel system relay, the soldering inside is kind of weak and causing an intermittent bad connection. Replace the relay or re-solder the bad connection. It would help to diagnose it more correctly if you could get trouble codes out of the ECM. Zee