Engine Performance problem
2000 Saab 9-5 4 cyl Front Wheel Drive Automatic

On morning start-up, smoke from the exhaust occurs sometimes. But after driving for a period of time,and stopping at a light, a cloud of smoke appears briefly and goes away. A grayish-white smoke with no real oil smell. Could this an overly rich mixture?

does it do it on the same stop? same time? temperature of engine?

The smoking is not always at the same stop, but only after complete engine warm-up.

it do it every stop after engine warmed?

notice any difference in vehicle performance, fluid levels?

Oil and coolant levels seem to be unchanged. If I'm stopped at a light for a period of time, it stalls after cylinder misfire. But immediately restarts, and the problem goes away for awhile. Never predictable.

it missfires and stalls also when this happens/ how long do you have to stop for it to do that?

i would be checkign for a vaccum leak, sticking pcv valve or hanging egr vavle first of all.