940 Turbo stalls randomly while driving
 

Started happening few days ago. Has happened 6 times now. Conditions have been: driving 20-30 mph and beginning to slow (not necessarily braking). All but 1 time was slowing, via coast, uphill (that 1 time was coasting downhill).
The dash goes dark only momentarily before illuminating again (as if key were turned on for accessories but not as far as ignition). I put the car in park and it starts with no issue.

I figure it must be bad wiring somewhere. First thing I checked was the battery connections - all solid with no wiggle/play in them. Given that the car starts fine, I'd rule out starter wiring.
I found no obvious visual indication of cracks, frays, etc. to wiring to alternator or distributor.

Experienced this before? Recommendations for next steps?

Model year = 1995

I'd start with the Crankshaft Sensor, then the fuel relay, both most likely culprits with the symptoms you describe.

Thanks very much.
Buying a new sensor today.

new OEM Sensor installed. Not the issue. Car stalled 3 times day after the install.
moving to fuel relay.
Alternator starting to have a bit of play in the pulley. Could that create a momentary loss of spark and thus stall?

does the battery light ever come on? not likely the alternator as these older cars can run off the battery (until it drops voltage).

When car stalls all dash lights illuminate. At stall, I simply put the car in Park and re-start, without issue.
battery light does not come on otherwise.
Must say that stalling in the center lane of the road during the commute to work is not fun.

Did you ever change the fuel relay? How many miles?

Car has about 175,300 miles.
Waiting of the fuel pump relay to arrive. Could not find it locally.
Hopefully will receive by the end of the week.

Clean and re-seat all grounds, even if they seem unrelated. I had a problem where when I switched from low to high beams on the headlights the motor would cut out for a split second (1992 740).

I unseated all the grounds up by the headlights, cleaned the tabs, then reseated them. Problem solved.

Finally changed the fuel relay 3 days ago. (our volvo parts specialist friends in Oregon provided the wrong part number. ended up having to place a second order with a different vendor)
Drove mostly on the highway since, without issue. This morning the car stalled again. Arrgh!

I will re-seat grounds as suggested above when I can get to it.

Thanks to all who have provided potential solutions.

I have finally changed the fuel relay - go the wrong part number from our friendly supplier in OR and had to order elsewhere.
Got by with couple days of driving before stalling again - same conditions: slowing from ~30 mph on a change of grade - flat to uphill or cresting a hill.

I have checked the major ground connections - though need to check those of headlights per dnarby.

The car has on a few occasions started to stall but actually didn't. During these the "check engine" light glows momentarily then all is fine.

While under the hood I noticed a few vacuum line could use replacement. Could ratty vacuum cause this under the conditions described?

ps - car has 175,000 miles