My girlfriend's car: '94 850 NA 5-spd sedan, 270k miles. It was owned by a volvo mechanic, it has always had meticulous service, motor shows even compression in all 5 holes, runs great usually.

Two months ago it started stalling at random. It will always restart after sitting for a period varying between 1 minute and half an hour. I have replaced the crank sensor and the cam sensor. The ignition computer even with new sensors shows the cam sensor "intermittent" code.

other things I know:

- fuel pump runs when cranking after it has stalled, fuel does not seem to be the problem to me. The computer does not run the injectors or the ignition in this condition.
- The tachometer drops to zero when it stalls even if the engine is still turning, ie. in 5th gear on the highway if the motor cuts out it is still turning at the same speed but the tachometer immediately drops.

does this sound like a bad ignition CPU to anyone? or maybe just bad wiring? anyone had a similar problem? Also a specific question: will this car run without the cam sensor, if not is it because the injection is sequential?

How do I test for a problem that only occurs once every hour or two of driving and only lasts for a few minutes? frustrating. I am a very good mechanic and electronics tech (audio specifically, but I understand theory very well), but I'm stumped here.