My 1996 850 wagon started a mysterious stalling about a week ago. It would studder and stall right after the engine reached normal running temp (about 15 minutes of driving). It would restart after letting it sit for about 10 minutes. The following morning it would not start right away, it took about 20 minutes to get it started, but the problems of the previous day returned. This lasted 3 days. I started to check the volvo forums on the web and deduced that it could be any number of things but decided to start with the fuel system. First I replaced the fuel filter, no improvement. Second I replaced the little grey fuel relay switch located on the radiator cowling, no improvement. Third I replaced the spark plugs, and cleaned all the electrical connections that I thought might be part of the fuel or spark system. Problem fixed. I'm not sure what worked but I thought I would contribute a success story. Many thanks to all who posted responses to stalling problems.