When it starts, does it belch out black smoke from the exhaust?
Does it do it when the engine is warm, or straight from cold?
Have you ever run it out of juice?
Does it start ok first thing in the morning?
Check all the vaccume hose connections, as the braded rubber hose's fail after a while,
I am not sure on the latest K-jetronic systems, but the idle air control valve may be stuck, the temp sensor for the warm up valve may be on the blink, the pressure regulator may be knackered too. (sorry the list is loooong)
Or, when was the last time you had it serviced? It could just be knackered plugs/leads etc?
Cheers
kraM