Hey Ben,

Doesn't sound entirely like the same problem, but within the last 6 months I had a very similar problem that might be worth trying. Intermittently while driving down the highway my 93 850 would automatically 'kill' or completely cut fuel from going into the engine. None of its symptoms were common with each instance and I pulled my hair out replacing 600 dollars worth of parts on multiple visits to more than one Volvo authorized mechanic before going to the service department and replacing one of the two fuel relays in the parking lot. 6 minutes and 57 dollars later she's never did it again.(I replaced the one found abutting the fire wall in a simalar compartment to the fuse box.) What is so amazing about this story to me...first that of all of the volvo mechanics I took it to all had heard of similar 850 problems but none had solved them. Second that something that was effectively a simple and common fuel problem was never properly diagnosed or even mentioned and lastly that I was crazy enough to buy parts like a crankshaft sensor in the belief that it might help me out.

I hope that this helps if not you then someone having a similar 850 issue. Good luck in your mystery problem.

Brian F.

Newburyport, MA

I'd guess that you have a wiring harness problem (wire rubbed through and intermittantly shorting out) and that it's being misdiagnosed.

There's two known troublesome wiring harness places that should be very closely examined, one is where the engine harness curves around the trans dipstick and the other (although I doubt it'd cause your problem) is where the dash harness crosses over the steering column (instrument cluster removed).

I've seen an early 850 (like yours) where a wire in the engine harness was intermittantly shorting on a sharp edge at the trans dipstick tube area and it too gave the ECU engine crank, cam sensor codes. That's where I'd suggest that someone looks very carefully (unravel conduit).