Just a small tip, or reminder; sometimes you really have to go back to basics, no matter how complicated a modern Volvo can be.

Had a 240 that would start, run for a few seconds then die. On occasion it cut out in traffic. Unpredictable, frustrating, and sometimes scary. After fixing, improving, and replacing all kinds of things, what made the car reliable once more was a locating and repairing a bad "push on" connector on the coil. The factory connector had developed metal fatigue and looked tight, but wasn't. Found it by wiggling various parts of the wiring loom, and BANG, all of a sudden the car started, and ran smoothly.

So, I cut off the old connector, cleaned the contact surfaces, crimped on a new (high quality) piece, a section of heat shrink tubing, and home again, home again, jiggedy-jig-jig.

Not saying that some of the other things didn't help; cleaning ground points, battery cables, fuses and their holders, etc., but this was decisive.

Those coils take a beating over the years, and are easily overlooked. Recommend that one carry extra connectors, and a crimping tool as part of an on-board tool kit. Hope this helps someone get back on the road.