Grey smoke from the BMW exhaust – what is the reason and how to fix it?

Driver’s question – gray smoke in BMW

The car when firing up in the morning smokes gray smoke for about 5 seconds. This is a symptom that does not occur every day. When there is no gray smoke, the engine runs quietly, and when it smokes the engine runs louder, which can be heard especially at the exhaust tip.

The oil level check indicates the maximum level, the engine is not taking oil, there is no coolant loss, and there is no oil. How to solve it?

The problem affected a BMW 3 with a 2.0i N20 gasoline engine, but it can also happen in other models.

BM Cars service response – N20 engine characteristics and gray smoke issue

The described problem of smoke kicking after starting a cold engine is a common symptom in 2.0i BMW gasoline engines. In the N20 engine there is a phenomenon of increased oil consumption. If the consumption does not exceed 1-2 liters per 10,000 km, then this is an acceptable level by the manufacturer.

The effect of burning oil can be the effect of a slight tinting of the exhaust gas to a gray or slightly blue color. This effect will be particularly noticeable after starting a cold engine for a few seconds, before the steam from the exhaust gas stops escaping from the exhaust system.

An additional source of oil getting into the combustion chamber can be a worn emphragm (oil separator) in the crankcase vent system. With a faulty emphragm, oil is pumped into the intake manifold and burned in the engine. The result can be a kicking up of the engine after starting and while driving after stopping the vehicle for several seconds (for example, at traffic lights). An increase in RPM when starting can be combined with the effect of blowing excess tinted exhaust gas out of the exhaust. In the N20 engine, the air purge is an integral part of the valve cover.

Taking into account the mileage of the car and the lack of taking significant amounts of oil, which you have found, we recommend checking the condition of the airfoil and the presence of oil in the intake manifold. If this is the case, you should replace the valve cover along with the airfoil and perform a cleaning of the engine intake system.

Other BMW tips related to the topic at hand

• Engine power drops and black smoke from BMW – how to fix it?
• Catalytic converter in BMW – problems and repair of catalytic converter in gasoline cars
• High oil consumption in BMW – what is the reason and what is the norm?

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