Just my 2 cent. but check the pos cable going from battery to starter. I had restart issues like what your talking about on my 2000 V70. and it was that cable. those cables and connections have been know to burn up and go bad.

You are correct about the OXS sensors, they go closed loop after a few minutes, after they heat up. First, are using OEM parts on all the replacements? The coolant temperature sensors (ECT) on these cars are known “ fussy” items on these cars How about. The last time the ignition system was serviced...

Good luck. It sounds like you have checked a lot of things and already replaced a lot of the parts that are the "usual suspects". As for the coil, one check would be to disconnect the wires and measure the resistance of the low and high sides during the time that the car will not start. Ac...

... For pre-1994 B5252S engines, the primary resistance is "not specified" and the secondary should be between 6000 and 7000 Ohms. How is that?! Ignition coils are ALL the same for ALL petrol 850 and s,v,c,xc70 (with cap & rotor)up to '99...and all have the same specs. In '99 with int...

Is your 850 10v or 20v car?
10v cars were not imported in U.S.
B5252 is 10v car.
Is CEL on?
Read the codes from A2 and A6.
'93 non turbo have two separate ecu(s) for engine(A2) and ignition(A6).
You have built-in diagnostic ports under the hood on ecu box.

Okay, I might have a suggestion, don't know if it will work for you. I had a similar problem with a friends Ford Sierra. He replaced pretty much all parts you mentioned. But the car wouldn't start with a warm engine. We got so desperate we went to our old teacher (from the mechanics school) for help...