If smoke is coming from your exhaust it's always a bad sign. Smoke simply won't emit from an exhaust when an engine is healthy, so if you notice smoke of any kind it is cause for concern! That said, don't confuse smoke with steam, which often may look like smoke especially on winter days. There are a range of different reasons why smoke would come from an exhaust pipe, so it's wise to know the facts before taking action.
The first thing to be aware of is that the smoke coming from your exhaust will smell different depending on the source of the problem. It is really important to find out why it is your exhaust is smoking so you don't waste time and money in the process of diagnosis and repair.
Blue smoke smells vaguely of burning toast, and you want to check the oil level if this is the case to ascertain if a low level of oil is causing the issue. If the oil is low simply fill it back up to the mark. As a general rule, it's incredibly important to ensure you are proactive about this issue by regularly checking the oil level in your car. If you notice your car continues to emit blue smoke it most likely means it needs new valve guide seals and/or piston rings - not good news for any punter!
White smoke is often the result of a leaky head gasket. You can diagnose white smoke by again following your nose - the smoke will smell a little sweet if you have coolant in your exhaust or a smell like burning oil if you use transmission fluid. Again, check the levels of these fluids to see if the engine has been overheating. You may also need to check the cooling system is working properly - if it isn't you may need to get a new head gasket.
If you notice black smoke coming from your exhaust make sure the automatic choke is working properly. This could also indicate that there is a problem going on with the fuel pressure, especially if your car is a more recent model.
