9 Causes Of Black Smoke From Exhaust And How To Fix It?

black exhaust smoke

Black smoke from the exhaust can become a serious problem if ignored for a long time, as it is a sign of malfunction or failure of some part in the engine. There are different reasons for white, black and blue smoke coming out of the exhaust pipe of the engine. The color of the exhaust smoke indicates different problems in the engine, so engine malfunction can be detected by looking at the color of the engine smoke.

In this article, we will learn in detail about the causes of black smoke coming out of the exhaust pipe, so that you will be able to solve this problem easily.

Why Does Black Smoke Come From The Exhaust – Causes

Black smoke coming from the exhaust means that fuel combustion is incomplete, caused by a clogged air filter, a faulty fuel pressure regulator, a faulty MAF sensor, bad fuel injectors, or a failed EGR valve.

These problems also occur if the fuel injector is sending too much fuel into the combustion chamber or the intake air valve is sending too little air.

For efficient operation of any internal combustion engine there must be proper ratio of fuel and air so that the fuel combustion process can be completed properly in the internal combustion chamber of the engine and power can be provided to the engine. But when the amount of fuel in the fuel mixture is high and the amount of air is low, the combustion of fuel inside the engine gets disrupted and comes out from the exhaust in the form of black smoke.

Let us know in detail the reasons for black smoke coming from the exhaust, so that you do not get confused if this happens in your vehicle.

1. Clogged or Dirty Air Filter

Clogged/Dirty Air Filter

Air enters the internal combustion chamber through the engine’s air intake manifold, which, when mixed with the fuel, makes it flammable. An air filter is installed in front of the air intake manifold to ensure clean air enters the engine. So that clean air continues to enter the air intake manifold through the air filter.

But when the air filter gets clogged with dust, less air starts coming into the air intake manifold. Due to this, the ratio of air in the fuel mixture starts decreasing, and due to the excess amount of fuel, the fuel combustion process in the internal combustion chamber of the engine starts getting disrupted, due to which black smoke starts coming out of the exhaust of the engine.

2. Faulty MAF Sensor

MAF Sensor

Sometimes, a damaged MAF sensor does not send the correct intake air quantity and speed signals to the vehicle’s ECU. As a result, the ratio of fuel and air in the fuel mixture is disturbed by the ECU, thereby disrupting the fuel combustion process in the internal combustion chamber of the engine. Due to this, black smoke starts coming out from the engine exhaust.

3. Double Washer in Fuel Injectors

Double Washer Issue in Diesel Fuel Injectors

Many times we take out the fuel injectors of a diesel engine for cleaning or repair and get one, two, or all of the fuel injectors cleaned or repaired. But sometimes, due to a mechanic’s mistake or to prevent the fuel injector from leaking, a double washer of aluminum or copper is fitted on the lower spray point of the fuel injector while fitting it into the engine head.

Due to which the fuel injector starts throwing the fuel on the piston in the form of drops instead of spraying, the diesel engine starts showing black smoke continuously when idling, and while increasing the speed, a lot of black smoke comes out of the exhaust.

This is the most important reason for black smoke coming out of a diesel engine. Which most vehicle mechanics ignore. The biggest symptom of this type of problem is continuous black smoke when you start your diesel vehicle from idle.

4. Faulty Fuel Injectors

Faulty Fuel Injectors

Fuel injectors are an essential and important component for every type of internal combustion engine, which release a spray of fuel over the piston in the internal combustion chamber of the engine, thereby igniting the fuel in the internal combustion chamber of the engine and starting the engine. goes.

But sometimes fuel injectors get clogged or, due to an internal fault of the fuel injector, fuel spray starts spraying in large quantities. This disturbs the ratio of fuel and air in the fuel mixture. Due to this, the fuel combustion process in the internal combustion chamber of the engine gets disrupted, and due to this, black smoke starts coming out of the exhaust of the engine.

5 . Incorrect Engine Timing

timing chain

If you have any general knowledge about engines, then you should know that any internal combustion engine has two main parts. “Engine Block and Engine Head”. The engine block consists of the crank, pistons, and rings. The engine head contains valves for air intake and exhaust gases.

The valve pistons in the engine head open and close at the right time according to their position, due to which the air from the intake valve enters the internal combustion chamber of the engine as per the position and requirements of the piston, and the hot gases are released by the right opening of the exhaust valve. exhaust into the internal combustion chamber of the engine.

This makes the fuel combustion process successful and complete in the internal combustion chamber of the engine. The valves in the engine head are opened by the camshaft according to the position of the piston, and the position of the camshaft is determined by the position of the engine’s crankshaft, with the timing chain or belt playing an important role.

But sometimes, during engine stroke or overhaul, the timing of the camshaft and crankshaft gets slightly mis-set, which disrupts the fuel combustion process in the internal combustion chamber of the engine and causes black smoke from the engine exhaust.

6. Faulty EGR Valve

Faulty/Clogged EGR Valve

Diesel engines are often equipped with an EGR valve. which is also called exhaust gas recirculation. The EGR valve recirculates small amounts of engine exhaust into the engine combustion chambers. so as to reduce the combustion temperature of the engine. This process reduces the formation of nitrogen oxides from the exhaust gases.

However, when the wrong amount of carbon dioxide is re-injected into the combustion chamber, EGR valves fail. because it is not able to control the growth of nitrogen oxides. So, the EGR valve starts to block and the exhaust is unable to circulate the gases into the combustion chamber. Due to this, there may be a problem with black smoke coming from the exhaust of the engine. For this, you can clean the EGR valve once. Also check the electrical function of the EGR valve.

7. Faulty ECU

Faulty ECM/ECU

The ECU is an essential and extremely important part of any vehicle. which can also be called the brain of the vehicle. The ECU smoothly activates every vehicle function. But sometimes there is some kind of fault in the ECU of the vehicle.

Due to which the functions of the engine can be badly affected. A bad ECU can throw off the fuel/air ratio in the engine’s fuel mixture. The combustion process in the engine starts getting interrupted and other functions of the engine can also be affected. Due to this, there may be a problem with black smoke coming from the engine exhaust. You can use an OBD digital scanner to inspect the ECU for any malfunctions.

8. Engine Carbon Deposits

engine head valve bent & worn

Usually, as the engine gets older, carbon and other inert substances start to build up in the engine’s combustion chamber. As the fuel burns, particulates build up on the fuel injectors and in the combustion chamber, and these particles get deposited in the piston and head valve of the engine.

Due to this, the ratio of fuel to air in the combustion chamber of the engine is disturbed. Due to this, black smoke starts coming from the engine. And these deposits can cause black smoke to come out of the engine exhaust.

9. Dirty Intercooler

The intercooler is located at the front of the vehicle’s engine. The turbocharger cools the engine’s exhaust gases with pressure through the intercooler and directs them back to the engine’s internal combustion chamber through the EGR valve.

This enables the fuel mixture to burn completely in the internal combustion chamber of the engine. But sometimes engine oil is collected by the turbocharger in the intercooler. Due to this, the intercooler may stop after some time and the recycled gas from the exhaust starts coming out directly from the exhaust. Due to which the problem of black colored exhaust smoke comes in the engine.

How To Fix Black Exhaust Smoke

There can be many different reasons for black smoke coming out of the engine, which should be investigated step by step to fix the problem. So that we can get rid of the problem of black exhaust smoke from the engine.

1. Clean or Replace Air Filter

Air filter is a useful component for engines. The air purified and cleaned by the air filter mixes with the fuel in the internal combustion chamber of the engine to make the fuel mixture ignitable. Due to this, the fuel in the engine burns easily and in full quantity and the engine starts and provides power.

But a clogged or dirty air filter reduces the proportion of air in the fuel mixture. which causes the fuel combustion process in the internal combustion chamber of the engine to get disrupted. Due to which black smoke starts coming from the engine exhaust. To troubleshoot the problem of black exhaust smoke, first of all, you must inspect the air filter of your vehicle and clean the air filter if it is clogged or dirty, or replace it with a new one if the air filter is too worn.

2. Replace MAF Sensor

Another reason for black exhaust smoke in the engine could be a faulty MAF sensor, or one of the wires at the MAF sensor could be damaged. Scan your vehicle with the help of an OBD digital scanner to inspect the MAF sensor.

If the MAF sensor is found to be defective or any wires connected to the MAF sensor are damaged, you must either replace the MAF sensor of your vehicle with a new one or repair or replace the damaged MAF sensor wire. Which can be helpful to stop black exhaust smoke from your vehicle.

3. Clean The Intercooler

The intercooler is located at the front of the engine of the vehicle. which looks like a radiator. But it is slightly smaller in size than the radiator. The turbocharger cools the exhaust gases of the engine through the intercooler with pressurization and sends them back to the internal combustion chamber of the engine through the EGR valve.

This enables the fuel mixture to burn completely in the internal combustion chamber of the engine. But sometimes engine oil is collected by the turbocharger in the intercooler, due to which the intercooler may get blocked after some time and the exhaust recycled gas starts coming out directly from the exhaust.

Due to which the problem of black exhaust smoke comes in the engine. That’s why always clean the intercooler at every service and close the hose pipe of Intercooler tightly. Due to which the pressure of turbocharger does not leak from anywhere.

4. Clean or Replace Faulty Fuel Injectors

Fuel injectors are an important component for the engine. Fuel injectors spray fuel into the engine’s internal combustion chamber above the pistons. Due to this, the fuel becomes flammable more quickly and completes the fuel combustion process inside the engine.

But sometimes the fuel injectors of the engine get clogged due to prolonged use without service. Due to the fact that the fuel injectors spray less fuel or due to clogged fuel injectors, fuel starts being thrown into the internal combustion chamber of the engine in the form of drops or leaks instead of spraying.

Due to this, the fuel does not become completely flammable and can cause black exhaust smoke from the engine. To fix this black exhaust smoke problem, clean the fuel injectors with a high-pressure machine or replace the fuel injectors with new ones if they are more worn.

5. Fix Intake Manifold Air Leaks

Through the air intake manifold, clean air enters the internal combustion chamber of the engine in proportion to the fuel, due to which the fuel mixture becomes flammable. But sometimes vacuum air leaks are due to burst or loose gaskets in the air intake manifold of the engine.

Due to this, the ratio of air to fuel in the fuel mixture starts deteriorating, the fuel mixture becomes weakly flammable, and the fuel mixture in the internal combustion chamber of the engine does not burn completely. Due to which the problem of black exhaust smoke starts coming in the engine. To get rid of the problem of black exhaust smoke from the engine, check the air intake manifold and fix it if it is leaking or replace the new gasket on the air intake manifold.

6. Clean or Replace EGR Valve

Often, black smoke in diesel engines is caused by a clogged or bad EGR valve. Because the EGR valve recycles the exhaust gases coming from the engine and sends them back to the internal combustion chamber of the engine, due to this, the gases from the half-burned fuel go back to the engine and burn.

But sometimes the EGR valve of the engine gets clogged or damaged. Due to this, the exhaust of unburnt gases does not happen again in the internal combustion chamber of the engine and these gases start coming out of the exhaust pipe in the form of black smoke. To troubleshoot black smoke in the engine, clean the EGR valve or replace the EGR valve with a new one.

7. Use Engine Additives

As the engine starts getting old. The burning of fuel in the engine’s combustion chamber then causes deposits of carbon particles or other substances on top of the engine’s pistons and in the valves of the engine head. which starts disrupting the fuel combustion process in the internal combustion chamber of the engine.

Due to this, black smoke starts coming from the engine. To get rid of the problem of black smoke in the engine, use the additive after some time in the engine. so that carbon and other substances deposited on the piston and head valve of the engine can be cleaned.

FAQ’s

Q. What does it mean when the exhaust is black?

Black exhaust means there is too much fuel burning in the internal combustion chamber of the engine. This can result in the fuel injectors spraying too much fuel onto the pistons or too little air entering the engine’s internal combustion chamber through the engine head’s intake valves. Due to this, the ratio of air to fuel in the fuel mixture has deteriorated.

Q. Why is my car blowing black smoke when I accelerate?

The fuel injectors inject a greater amount of fuel into the engine’s internal combustion chamber whenever acceleration is accelerated or the fuel mixture does not burn completely due to a clogged air filter, a bad fuel system, or a clogged air intake manifold, due to which black smoke can be seen during acceleration.

Q. Is it safe to drive with black smoke from the exhaust?

No, it is not safe to drive a vehicle with excessive black smoke. because black smoke from the exhaust of the vehicle indicates some fault in the engine. This problem should never be ignored for a long time.

Q. Can black smoke cause misfiring?

Yes, black smoke can come from the exhaust of the engine due to an engine misfire. Because the combustion process is interrupted to misfire the engine, due to which the fuel mixture does not burn completely.

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