I think this is related to the idling/servo motor in your AC compressor. Don't know the exact parts description but I have the same problem with my '99 Mitsu Galant - shark model(4G63. carb. type) when I turn on my AC, the idling goes so low and jerking. Eventually the engine dies (unless I step hard on the gas to pump up the revs) and have to restart again. I think this is a common problem for all Mitsu cars.
'Hope some techies here can share more infos on how to solve this recurring problem?