If you notice smoke coming out of your Audi A4 exhaust, know that the engine of your vehicle may have a failing component. You can diagnose the issue based on the smoke color. The white smoke emitted by the exhaust when you first start the engine in the morning is no big deal as it’s just water vapor. But if you see the smoke even after the engine has warmed up, there is a problem to fix. In this article, we are going to find out why your Audio A4 is emitting white, blue or black smoke. We will also talk about how you can fix these issues. Read on.