Have you started noticing some black exhaust smoke from the rear of your car or truck? Well, this might be worrying. But you shouldn’t worry because we are here to help you out in tackling this problem quickly and effectively.
Having a problem like this can be a really frustrating thing to deal with. Namely, out of two reasons. It indicates a problem that you need to solve. Having a smokey car can only mean one thing, some of the components inside of your engine or exhaust system are probably worn out and in desperate need to be serviced or replaced.
The second thing is that you annoy other people on the road. Nobody loves smokey cars and you will definitely piss people off. And the police will definitely keep an eye on you if they notice how your car is smoking like a chimney as you’re driving on the freeway or even in town. So, you don’t want to drive a car like this because of these two reasons. You need to start looking for a solution to this problem. But you shouldn’t worry because we are going to help you out with that.
First, we will cover what is back exhaust smoke and learn more about this problem. Then we will take a look at how serious it is and then we will discuss the reasons for black exhaust smoke. Later on, we will move in with diagnosing and sorting out the issue. So, if you want to learn more when it comes to this problem, follow along.
What Is Black Exhaust Smoke?
Now before we dive deeper into the problem of black exhaust smoke. Let’s first elaborate on the problem. This would be quite useful for beginners who don’t know what black exhaust smoke is and want to learn. If you feel like you are well prepared, you can move to the reasons why this problem happens. If not, keep up with us for a bit while we cover this stuff.
Nevertheless, black exhaust smoke is a visual representation of a problem. This means that your car is suffering and has some issues.
On diesel cars or trucks, a little black smoke is a completely normal thing. Especially in older models. But in modern gasoline cars (oh, and if you’re keen, do check out our guide on what color is gasoline), this isn’t right. It means that there is some problem with the engine or the ignition of the fuel. As well as the emissions equipment.
The engine health is really poor since the engine produces any kind of smoke, it doesn’t mean that it is white, blue, or back exhaust smoke.
When this happens to you, it is advised to evaluate the circumstances under which this black smoke occurs. Whether it is when you press hard on the throttle or when the car is idling.
This is essential to estimate whether the problem comes because of poor catalytic equipment or because of the engine itself.
In addition to this, the smoke smell is really important (with some help in understanding how to get rid of smoke smell in car and how to get smoke smell out of car). A rotten egg smell for example (you can learn more in our guide on my car smells like rotten eggs) can indicate problems with the catalytic converter. While a smell of gas coming from the exhaust can indicate a problem with the ignition.
That’s why it is very useful for you to take these things into consideration when you decide to jump and diagnose the issue of black exhaust smoke. Now let’s discuss more about the problem.
Is This Black Smoke A Thing Of Concern?
After we elaborated more on the problem of black exhaust smoke. Now let’s see if this black smoke should be a real concern and whether or not you should be alerted by this symptom that your car is producing.
And the answer is yes, black smoke from exhaust indicates that there is a problem and this problem requires a proper solution.
The level of smokey-ness from the exhaust will tell you a lot about whether or not you should be really alerted.
If the exhaust smokes when you press on it really hard, then this is normal. Especially for diesel engines or older cars that are drinking oil. So, you shouldn’t be worried that much in this case.
But if your rear bumper is all black from the smoke that the car produces on a daily basis, then yes, you should be alerted and try to solve this problem.
As you know, when this happens there will be considerably more emission gases released by the vehicle. Resulting in poor performance in emission testing when you register the car. So, if you live in a state that is very strict when it comes to this like California or New York, you can expect to fail the emissions test.
In addition to this, you can get pulled over by the police and fined because you are maneuvering a vehicle that is not in road-worthy condition. In this case, you will be ordered to return the car to the factory spec by fixing the problem if you want to continue driving the vehicle. That’s why black exhaust smoke should not be ignored and you should try to find a way to fix the issue. But how you can do it? Let’s discuss the reasons why it happens first.
Causes Why There Is Black Exhaust Smoke
Now let’s focus on the reasons for the black exhaust smoke and cover them in-depth. This will be quite useful information for you. Because if you know the causes, you will be able to act accordingly and try to solve the problem quickly.
We are going to cover both types of engines, diesel, and gasoline since both of these types are known to smoke and cause trouble for their owners. So, what are the reasons why the black exhaust smoke problem occurs? Let’s elaborate.
Black Smoke In Gasoline Engines
First, let’s cover the black smoke in gasoline engines. These engines are not that plagued by black smoke but it knows to happen when some of the engine components are broken and are malfunctioning. So, what are these causes? Let’s see.
1. Broken Catalytic Converter
The first and most obvious reason for black exhaust smoke in gasoline engines is the broken catalytic converter.
As you probably know, the catalytic converter is a device that is there in order for your vehicle to meet the emission standards. Whenever the catalytic converter is not performing as it should. The vehicle will smoke from the rear.
There will be black smoke coming from the exhaust along with that rotten egg smell that is really common when this component fails. This smell happens because the fuel contains a small amount of sulfur, and when the catalytic converter is not working, the sulfur will not get burnt and will be released into the atmosphere. Something that is not ideal.
Black exhaust smoke along with this rotten egg smell is a dead giveaway when there is an issue with the catalytic converter. Now, let’s move to the next probable cause for black exhaust smoke.
2. Broken MAF Sensor
A broken MAF sensor can also cause black exhaust smoke. As you probably know, the MAF sensor is in charge of maintaining the right air to fuel mixture.
So, when this sensor fails, there could be too little air sucked into the engine. This will result in rich air to fuel mixture.
When the car runs rich, you will be able to tell by smelling the exhaust gas. This smell will also be present inside the cabin.
If you notice a gas smell (to learn more, head over to our guide on how to get gas smell off hands) and black exhaust smoke coming from the exhaust. You know that there is a problem with some of the sensors that are in charge of the fuel to air mixture. Always note this clue and you will be able to quickly diagnose a problem with black exhaust smoke and the smell of gasoline. Now let’s move to the next probable reason for this problem.
3. Broken O2 Sensor
Another very probable reason why you can have black exhaust smoke on your vehicle is because of a broken O2 sensor.
As you probably know, this sensor is measuring the exhaust gases. There are two of them. One before the catalytic converter and one after the catalytic converter.
They tend to fail and develop issues like in our case with the black exhaust smoke. This is the case because they are giving false readings to the ECM and the ECM cannot adjust the fuel to air mixture.
So, symptoms like black exhaust smoke and other very unpleasant symptoms are very common. If you run your car like this, you also risk ruining the catalytic converter. The catalytic converter will get clogged with gas deposits and will not function. Causing your car to stall eventually. So, beware of this sensor. It is better to spend $200 to replace it rather than spending $1,200+ on a new catalytic converter (as is the case with a 2000 Jeep Cherokee catalytic converter).
4. Oil Consumption
The last probable reason why you have black exhaust smoke is because of increased oil consumption. This increased oil consumption is caused by problems inside of your engine.
Namely, the oil rings on the pistons are not sealing well. Resulting in oil consumption. The oil passes between the pistons and the cylinder walls and ends up in the combustion chamber.
Whenever there is oil in the combustion chamber, the oil will burn and black exhaust smoke is quite imminent. Whenever you notice that you lose oil and your engine is smoking. Your best bet would be to pour some thicker oil that will seal better.
If this doesn’t work, you will have to perform an engine rebuild pretty soon. The rings will have to be replaced and the engine will be refreshed. It is better to do a mild refresh like this than leaving it like that.
If you decide to leave it like this and you forget to top off the oil. Your engine will be quite prone to increased wear and tear. The more wear and tear, the closer the engine is to the junkyard. That’s why always top of the oil when you notice that the engine is losing the oil and black exhaust smoke is coming off from the car.
Black Smoke In Diesel Engines
Now let’s discuss what could cause black exhaust smoke in diesel engines. As you probably know, diesel engines are a bit different and can smoke a lot more than gasoline.
Namely, because of the diesel fuel that is used to power these machines. This fuel is not that eco-friendly and produces a ton more particles than your regular gasoline engine. But what are the causes for black exhaust smoke from diesel engines? Let’s elaborate.
1. Causes Shared With Gasoline Engines
Now first before we cover the reasons for black exhaust smoke on diesel engines. Let’s address the ones that are shared with gasoline engines. Since both of these are internal combustion engines and share a similar architecture.
So, in diesel engines, black exhaust smoke can also be caused by a bad MAF sensor which is the sensor that regulates the fuel to air mixture. Then the second very common thing is the oil burning problem that also causes the black exhaust smoke in diesel engines as well.
O2 sensors also can cause black exhaust smoke. Basically, all of the same things can cause problems on gasoline except the catalytic converter. Diesel engines do not have a catalytic converter but rather something called a DPF, which we are going to cover in the following chapters where we will elaborate on the black exhaust smoke reasons on diesel engines.
2. Bad Fuel Injectors
One common problem with diesel engines is their fuel injectors. These injectors are not like your regular gasoline injectors that rarely break. Diesel fuel injectors are really expensive machinery that requires a lot of precision.
These injectors help with a high-pressure fuel pump that delivers the diesel fuel with extreme force. But they have a downside. They are really sensitive to bad diesel fuel or after they accumulate a lot of miles they are known to break.
Whenever diesel injectors fail, they develop a ton of symptoms. Including the black exhaust smoke. If an injector fails will not perform as it should.
So, when it comes to this, there should be some diagnosing to be done on this engine to determine which injectors are faulty and see what could be done about them. Now let’s move to the second probable cause for black exhaust smoke on diesel engines.
3. Clogged EGR Valve
The second probable reason that could cause black exhaust smoke on a diesel engine is the bad EGR valve. These EGR valves are installed on diesel engines for emissions. More precisely, they stop the NOx particles from escaping into the atmosphere.
How they work is really simple, they transfer some of the gas again into the intake manifold so the NOx gases are completely neutralized.
These EGR valves are notorious for clogging up carbon deposits. And when they clog up, you are basically facing black exhaust smoke symptoms as well as check engine light on the dashboard. Either way, not a good situation.
So, this problem needs to be thoroughly diagnosed and the problem to be sorted out fully. But if you have an OBD2 scanner you can do this really easily. We will cover that later in the article after we finish with the probable reasons for black exhaust smoke in diesel engines.
4. Clogged DPF Filter
Another very common reason for black exhaust smoke on diesel engines is the broken diesel particulate filter, also known as DPF.
This filter is one of the standard equipment that every diesel vehicle has. This DPF filter is installed on the exhaust and it basically destroys the NOx particles. Similar to the EGR valve that redirects gases into the combustion.
But the DPF is the last line of defense to annihilate any remaining pollutants. Not that there are no pollutants that escape in the atmosphere. But the most important ones are the NOx particles are to a big extent neutralized.
So, what happens with the DPF filters is that they are used for driving in the city too much and they clog up. Whenever they clog up they are difficult to clean and if the driver is not aware of this clogged DPF, the honeycomb that is inside of it will get crushed. And whenever there is no honeycomb structure inside of the DPF, there will be black exhaust smoke.
Some people even remove these DPF filters just to have that rolling coal mod. This is not okay in my opinion since these vehicles pollute a ton more than vehicles with the proper emission equipment.
But some states allow it. Anyways, whenever you notice black exhaust smoke coming from your car or truck, this might be because of the diesel particulate filter that got clogged up. Now, let’s move to the diagnosing process of these problems and see what you could do to diagnose black exhaust smoke.
How To Diagnose The Problem Of Black Exhaust Smoke?
We learned all the possible reasons and causes for black exhaust smoke. Now let’s focus on how to diagnose the problem of black exhaust smoke. How you can pinpoint the exact cause for this issue that is happening in your car? Let’s see.
The first thing you need to do is to inspect the vehicle and see when it starts to smoke, if it’s smoking all the time or it smokes when pressing on the gas pedal. Also, beware of the oil level inside of your engine and if the engine is drinking oil, then this might be the cause.
Whenever this happens there will be black smoke. Also, if the exhaust fumes smell like gasoline, then you can bet that the car has either a bad O2 sensor or a bad MAF sensor.
In this case, you need to take things further and diagnose the problem with an OBD2 scanner tool. With this tool, you will get the right input and data you need to estimate what are the problematic components.
You need to study these errors and then based on this input you will need to troubleshoot the matter to determine what is the real problem and pinpoint the issue.
How To Fix The Problem?
Fixing the problem of black exhaust smoke really depends much on what is causing the issue. Before this issue is able to be fixed, proper diagnostics have to be performed and proper troubleshooting as well.
So, if you are not experienced with working on cars, you might want to leave this problem for the mechanics to deal with.
Even though I encourage everyone to have an OBD2 scanner and scan the car whenever there is a problem. By doing this, you will be safe from mechanics who want to fool you and trust me, there are plenty of mechanics that will try to do that while fixing your black exhaust smoke or some other problem.
Cost To Fix Black Exhaust Smoke?
So, what is the total cost of fixing this problem with black exhaust smoke? Well, it really depends on what is causing the issue after all. Different problems require different and more expensive solutions than others.
The cheapest solution will probably be a sensor that could be purchased for $150 to $250 and replaced. EGR valves are a bit more expensive and could cost about $300+.
Catalytic converters and DPF filters are really expensive. The price for this is $1,200+ and the cost sometimes goes up to $2,500.
And the most expensive job is probably if the engine drinks oil and this causes the black exhaust smoke. This problem will require a ton of money to be sorted out. $3,000+ in worst cases. Sometimes it is just better to purchase a used engine with low miles than to spend money on this engine. But that’s just my opinion.
Facts: Common Causes of Black Smoke from a Diesel Engine and How to Fix It
- Black smoke from a diesel engine indicates that there is a problem with the engine, such as an imbalanced fuel and air ratio or a more complicated issue.
- Diesel engines should not produce almost any smoke while working, but it’s normal for some older diesels to release some smoke when accelerating under load.
- The most common causes of black smoke from a diesel engine include a dirty air filter, faulty injectors, a dirty EGR valve, and a faulty MAF sensor.
- A bad fuel/air mixture is usually the cause of black smoke from a diesel engine exhaust.
- To prevent further damage to your car, it’s important to take care of any issues as soon as you notice anything wrong.
- You can ask a specialist at an authorized dealer for help with any problems with your diesel car.
- Cleaning or replacing a dirty or clogged air filter is important to ensure that the right amount of air is reaching the engine.
- Checking the engine rings in an auto repair shop and replacing them if necessary can prevent black smoke from the exhaust.
- Having the fuel pump and injection system inspected by a professional mechanic and upgrading them with a common-rail injection system can prevent incomplete combustion and reduce black smoke.
- Mixing diesel fuel with a high-quality fuel additive can prevent the formation of deposits in the engine and reduce black smoke emissions.
Conclusion To Black Exhaust Smoke
In this article, we have covered quite a bit when it comes to the problem with black exhaust smoke. First, we elaborated on the issue and whether or not is alarming for you as an owner, and how you should react.
Then we covered the reasons and causes why this problem happens in both gasoline engines and also in diesel engines. In gasoline engines, this is mostly caused by increased oil consumption or a sensor issue. While in diesel engines it could be caused by a bad EGR valve or a bad DPF filter. Please note that some gas engines also have EGR valves, so beware of this.
Lastly, we focused on diagnosing and sorting out the issue and normally, at what cost this is possible.
These tools have been tried and tested by our team, they are ideal for fixing your car at home.