I have '99 SSE with 3800 series II NA engine that will misfire / run rough for several moments after a warm start, then it will rev itself up to around 2,200 rpm and smooth out - then run fine. A few times it would run so poorly it will stall, then I wait a bit for the engine to cool off more before trying again. It is not on every warm start, but the majority of them. When it is misfiring it really does not respond to the throttle.
Have not had the problem if the engine gets good and cold, but running errands around town is a pain.
Any suggestions? I was thinking to start with the coils, but wanted to ask here first in case others had already had (and solved) this issue. Found out a friend of mine is having the same issue with his LeSabre.