I'm thinking of buying a 95 940 for way cheap as a backup for my aging other Volvo. (Prospect has a B230FD and only 137k.) But I need to ID an engine problem as fixable or not. It starts and idles fine, but sounds like a diesel. I guess in all my B230F experiences I've never had one with piston slap, and I thought these later B230s had largely solved that problem.

So - what - a rod bearing at 137k? I disconnected plug wires one by one and No. 1 disconnected took away the diesel sound. But the sound resumed when I reved it up. Does this sound like a rod bearing symptom? I see from the FAQ that you can replace rod bearings without an engine R&R, so I'm not too intimidated.

What do you think? Price is very attractive. Price going in is, that is.....

Have not done a compression test yet, to be continued.

Define attractive. I brought my last 2 940s in the last 8 months for well under $2k, both under 100,000 miles and excellent condition. So an $800 complete engine rebuilt in parts and machine shop charges should be considered in your decision assuming you don't count your labor.

But on the up side, you'll have a new engine.

PS Use a good machine shop which is not always the one the dealer uses, I learned the hard way.

Asking price is 500, but I would offer somewhat lower. And I'm kinda itchin to rebuild a Volvo engine using a good machine shop and my own labor - I had fun and good success on 544s and a 122S, well, some time ago. My only hesitation is about the complexity and newer procedures/special tools I may not be familiar enough with. Been doing everything on our 93 940 with high miles, and I haven't been confronted with anything mystifying.

I think what you describe could be rod bearings, yes. Good method, taking off the wires so it's localized. The 95 is a good car and has all the improvements, so maybe take your old motor and put it in this car, or take some time and rebuild the 95. I'd take that car, myself. A motor is just not that off the charts, to get or to do.
Although it may be 'possible' to do rod brg in the car, I'd not want to do it as the crossmember is gonna be in the way, and you don't know the rod journal condition either. The crank almost certainly should be turned IMO.