Nguyên nhân và cách khắc phục khi ô tô nhả ra khói

If on a cold winter morning you start your car and see a faint trail of smoke coming from the rear, don't worry, it's probably just condensation in the exhaust pipe getting heated and evaporating.

But if you live in a hot climate or your car is on the road, smoke is obviously not a good thing. Let’s go over the main reasons and what to do when you find yourself in such an unexpected situation.

1. Blue smoke

The bad news is that the engine is burning oil, which happens when the valve seals (also known as cup seals) or piston rings are loose and the cylinder is damaged, allowing oil to leak into the combustion chamber. Burning oil can cause oxygen sensors to fail, and the engine's lubrication system may have low oil levels and not have enough oil pressure to function.

In reality, blue smoke is quite rare, but if you are unlucky enough to fall into this situation and continue to move, it is likely that the engine will be seriously damaged, especially on long trips or when on the highway. So you should be alert, consider, check and take accurate action to protect your car.

Cách xử lý:

When encountering this situation, it is obvious to smell the burning oil smell, then you should check the oil level through the dipstick, if the oil is lower than the recommended level, you should add it immediately. Do not let the engine work without lubricating oil, this will lead to more serious damage such as piston stuck in the cylinder.

After that, a general check of the engine is needed, from measuring the lubricating oil pressure, checking for oil leaks under the crankcase, valve rubber seals, piston rings and cylinders. Damaged parts need to be replaced or repaired, or even the engine overhauled.

2. White smoke

CarWhite smoke from a car can be caused by a gasoline engine burning coolant or transmission fluid. The main cause is a leaking engine head gasket or a cracked engine head that prevents the combustion chamber from being sealed, allowing coolant and transmission fluid to leak into the gasoline engine and mix with the fuel, creating white smoke.

For diesel engines, when white smoke is emitted, it may be due to coolant entering the combustion chamber like in gasoline engines or fuel not burning completely. The cause is due to the injector working at the wrong time or one of the cylinders not having enough compression pressure. Accompanying the white smoke will be a damp smell due to the coolant burning and evaporating, or the unpleasant smell of burnt gearbox oil.

How to handle:

When you see white smoke coming from your car, you need to determine whether the cause is due to condensation in the exhaust pipe or not. If it is not due to condensation in the exhaust pipe, you need to check carefully and “first aid” immediately to minimize more serious risks that may occur to your car.

When the injector works at the wrong time or one of the cylinders does not have enough compression pressure.

If you see white smoke with an unpleasant damp smell due to the coolant burning, evaporating and burnt transmission oil. At this time, you need to check the coolant level and transmission oil level to determine the exact cause and handle it promptly.

Check cooling system pressure if radiator is low and engine is overheating, and replace engine head gasket if necessary.

Add coolant and transmission fluid immediately before proceeding with the repair steps. If necessary, take the car to a garage for a comprehensive check, to avoid a bad situation happening to the car.

3. Black smoke

This is the most common form of smoke on the road, and unlike the two cases above, you can still complete your journey and stop by the garage afterwards because this is not too serious and can be fixed relatively simply.

In old diesel engines, black smoke is an indispensable part when starting or under heavy load, but this is completely "abnormal" with car models or pickup trucks with "clean diesel engines" (using electronic ECU control and Common rail fuel injection system). The reason is that the engine receives too much fuel than needed: due to the injector working at the wrong time or the controller having a problem.

In addition, black smoke appears in gasoline engines because the air-fuel mixture is too rich and the combustion process is not complete (too much fuel, not enough air), especially when the vehicle is under heavy load. If black smoke appears frequently and a thick layer of soot accumulates under the exhaust pipe, it is clear that the engine is taking in more gasoline than necessary.

In gasoline engines with carburetors, rich fuel and black smoke can be caused by a faulty throttle body, metal or plastic in the carburetor, a low fuel float, and a dirty fuel filter. In modern fuel injection systems, black smoke from the exhaust comes from one or more leaking injectors, excessive injection pressure, a faulty oxygen sensor, or a miscalculated control unit.

Cách xử lý:

Nếu động cơ sử dụng bộ chế hòa khí, khi gặp tình huống này, bạn cần kiểm tra tình trạng của bướm gió tự động hoặc phao xăng đồng thời có thể thay mới nếu cần thiết.

Nếu động cơ của bạn là hệ thông phun xăng nhiên liệu, bạn cần kiểm tra áp suất xăng hoặc dầu, kiểm tra lọc gió có sạch sẽ hay không, đồng thời lái xe của bạn vào khu dịch vụ để họ kiểm tra chi tiết hơn, như các cảm biến và cụm kim phun.