idle AND running issues!
 

I recently purchased a 1987 BMW 325(e). The car will start, runs great for a while, then stalls. Symptoms include loping idle, white smoke (smells like rich burning fuel), then finally shuts down. If I wait a little while, the car will start just fine. It will run for a while, like it should, then starts blowing smoke again. This takes place at random time intervals. I could go 10 or 50 miles before it does it again. I have changed the O2 sensor, new plugs, and it ran great! About 40 miles later, it started doing all this. I have started the car every day since then, sometimes it runs, sometimes it dosent. Any help would be appreciated.