A4wheelin

It cranks for like 5 or more seconds then when it finally turns over the revs are bouncing around up to about 2k. White/blueish smoke out the tailpipes. And the revs take about 2 minutes to finally settle to their normal 900rpms at idle. What's the deal? I'm trying to sell my car and this isn't going to help at all. Other than that it runs perfect, and doesn't do this except at start up every few days or so. Thanks.