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What Does Black Exhaust Mean?

What Does Black Exhaust Mean?

We’ve all seen it before: a stream of black smoke exiting the exhaust pipe of a car or diesel truck. It’s easy to spot when coming from the vehicle in front of us. Yet, it’s most important to understand what this means to properly maintain our own vehicles. What is black exhaust? Continue reading to find out!

What Black Exhaust Means

Think about when you get up in the morning – the perfect mix of black coffee, sugar, and milk gets you energized. In the same way, an engine needs the perfect mix of fuel, oxygen, and heat. Black exhaust occurs when the engine receives too much fuel and not enough air. In this article, we’ll answer the following questions: which car parts aren’t working correctly, and what can be done to solve this?

Air Filter

When clean, the air filter should be white or off-white in color. Over time, it will become clogged by contaminants, and not enough air can get through. You’ll know to check your car’s air filter when black smoke comes out of the exhaust. This is excess fuel, and in this case, your engine is trying to compensate for the lack of air by using more fuel to maintain its normal speed.

Fuel Injector

Fuel injectors are engineered to deliver a mix of fuel and air to the cylinder. The fuel is ignited, creating an explosion that produces power and, ideally, the least amount of dirty exhaust as possible. However, if the fuel injector is not closing fast enough or is not closing at all, fuel will leak into the cylinder, giving off more fuel and less air. This will cause black smoke to appear when increasing the speed of your car.

Fuel Pressure Regulator

As the name implies, the fuel pressure regulator is responsible for regulating the pressure of the fuel. Too weak, and there won’t be enough power. Yet, there is a fine line; if the pressure is too strong, it could damage the engine. A fuel pressure regulator that’s not working correctly can increase the fuel pressure, resulting in more fuel and less air.

Intake Air Temperature Sensor

The intake air temperature sensor (IAT sensor) monitors the air temperature. It sends this information to the electrical control unit (ECU), a part of the car’s computer that will change the air/fuel ratio accordingly. So, if there’s a warmer air temperature, it’ll inject less fuel, and if there’s a cooler air temperature, it’ll inject more fuel. A faulty sensor will provide the ECU with inaccurate information, which could result in too much fuel and lead to black smoke.

Mass Air Flow Sensor

Here’s another sensor to check if you see black exhaust coming out of your car. The mass air flow sensor (MAF sensor) detects how much air is going into the engine. A bad sensor will give the computer the wrong information, making the computer think more air is going into the engine than in reality. When this happens, extra gas is used.

Manifold Absolute Pressure Sensor

The following sensor on our list is the manifold absolute pressure sensor (MAP sensor), which calculates the air pressure in the intake manifold, a series of tubes that evenly distributes air to each of the cylinders.  A faulty sensor will provide the computer with the wrong information and send more fuel into the combustion chamber. That is the part of the cylinder where the fuel and air are ignited.

Upstream Oxygen Sensor

Last up is the upstream oxygen sensor. It reads the oxygen content in the exhaust and sends this information to the computer. An excess of oxygen will trigger a low voltage, and a lack of oxygen will trigger a high voltage. This is done in an effort to regulate the air/fuel mixture. If it’s not working correctly, too much fuel can be used.

What Steps Should I Take?

If black smoke is coming out of your car’s exhaust, it’s important to identify why this is happening. Your mechanic should be able to help you correct it before a larger issue occurs. While HSO may not be able to handle this issue, you can count on us for your gasoline or diesel fuel needs. At HSO, we deliver bulk fuel to our customers and offer a range of top-quality name brand products in gas & fuel additives, diesel exhaust fluid, and many more. Call us today at 1-800-467-5044 or visit us at to get started!




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