Like it or not, the internal combustion engine in your car produces a lot of harmful gases. Thankfully, the auto industry has made significant advancements in emissions control to, well, control these harmful gases. However, an emissions system problem can occur as the car ages.
Not only the car will produce more harmful gases when an emissions system problem occurs. But it can also affect your car’s performance. This post will let you know everything about your car’s emissions control system:
Emissions System Problem: What Is An Emissions Control System?
Your emissions control system consists of several devices working together to reduce the amount of harmful gases that come out of your car. Here are the devices that make up the emissions control system (if you want to learn more, check out our guide on do all cars have a catalytic converter):
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- Positive Crankcase Ventilation (PCV) system.
- Evaporative Emission Control system.
- Exhaust Gas Recirculation (EGR) system – mostly only present in diesel engines.
- Secondary Air Injection system.
- Catalytic Converter.
- Exhaust Pipes.
These six components work together to reduce the amount of harmful gases that come out of your tailpipes. To understand why and how it can affect your car, we need to talk about how each of these devices works:
1. Positive Crankcase Ventilation System
To understand the PCV, you first need to understand the basics of an internal combustion engine. Don’t worry, we’ll try to make it as simple as possible:
Your engine uses fuel and air to drive a series of pistons upwards and downwards. These pistons then drive a crankshaft that sits underneath it. Then through a series of gears and drive shafts, it drives the wheels to move your car.
Ideally, the fuel and air mixture should combust on top of the pistons. However, some of the fuel and air can manage to slip through the pistons which then enter the crankcase – the structure that encases the crankshaft.
This isn’t ideal since the fuel and air can induce excess wear on the crankshaft. Additionally, it also simply circulates the excess air through the exhaust system which increases emissions. This is where the PCV comes in:
In the simplest term, the PCV monitors the amount of gas in the crankcase. It then can open a valve to let these gases escape, recirculating them back into the engine. So, rather than wasting the gas and polluting the atmosphere, it takes these gases back into the engine and reuses them.
For some additional information, the PCV works along with your car’s Mass Air Flow (MAF) sensor to control the amount of gas to recirculate. This means the PCV is not only a part of the emissions control system but also a part of the air intake system.
2. Evaporative Emission Control System
The PCV is one of the more complex devices to understand. Meanwhile, the evaporative emission control system – or EVAP for short – is relatively simpler.
It’s essentially a system that controls and prevents fuel vapor from escaping the fuel system. Rather than letting them escape and pollute the atmosphere, it traps the fuel vapor using a charcoal canister (aka the EVAP canister).
3. Exhaust Gas Recirculation System
As the name suggests, the EGR system recirculates exhaust gases back into the engine. Seems pretty straightforward, no? Rather than letting the exhaust gases escape through the exhaust pipes, why not use them to power the engine again? But it’s actually more complex and cleverer than that.
By recirculating the exhaust gases and mixing them with air, it lowers the oxygen level inside your engine. As a result, your engine can combust the fuel and air mixture at a lower temperature. And a lower combustion temperature will result in lower Nitrous Oxide (NOx) levels. Needless to say, NOx gases are very harmful to the environment.
NOx gases are a big problem in diesel engines. They inherently produce more NOx gases as they run hotter than gas engines. This is why EGRs are more common in diesel engines. However, many modern gas engines also use EGR to help reduce emissions (just like what is the purpose of a catalytic converter) and make them more fuel-efficient.
4. Secondary Air Injection System
Unlike the other systems we’ve mentioned, the secondary air injection does not work with the engine. Rather, it works with the exhaust system. The system consists of a pump and a valve.
The simplest explanation is that this system injects fresh air into your car’s exhaust system. The pump will suck in air when necessary, and then the valve will open when the Engine Control Unit (ECU) deems it necessary to pump air into the exhaust system.
The purpose of the system in modern cars is to help warm up the catalytic converter so it can be more efficient. Additionally, the system usually operates during cold starts. This is because, during cold starts, your engine needs to burn more fuel.
This results in a richer fuel and air mixture, and more harmful exhaust gases. As mentioned, the system warms up the catalytic converter to make it more efficient. But it also helps to induce secondary combustion in the exhaust system, leading to slightly less harmful gases overall.
5. Catalytic Converter
This is arguably the most important component in your car’s emissions control system. Unlike the other components that focus on recirculating vapors and exhaust gases, the catalytic converter’s job is to filter these harmful gases before it escapes the exhaust system.
The catalytic converter works by using valuable metals such as platinum, palladium, and rhodium. These metals are rare and valuable, which is why catalytic converters are valuable and thieves often go after them.
Anyway, when exhaust gases enter the catalytic converter, it catalyzes a redox (oxidation-reduction) reaction which cleans the exhaust gases. The resulting exhausts gases are still harmful, you definitely don’t want to breathe them in. To learn more, check out our explainer on what’s a catalytic converter made of and what is in a catalytic converter. However, it’s much cleaner than before it enters the catalytic converter.
Since it has to filter out these harmful gases, the catalytic converter can clog up as the car ages. In some cases, you may be able to unclog them by cleaning them. However, in some cases, you have no choice but to replace them. A catalytic converter will typically last for about 10 years.
6. Exhaust Pipes
The exhaust pipe, as we’re sure you’re aware, is a series of pipes and tubing that allows exhaust gases to escape. It consists of the exhaust manifold, which is a series of tubing that comes out of the engine. And then it connects to the front pipe and into the catalytic converter.
The catalytic converter usually sits – or hangs to be accurate – in the middle of the car. It then has another pipe that connects to the muffler, a device to control the sound output of the engine. Then it will finally lead to the tailpipes where the exhaust gases will escape.
The exhaust pipe is there to allow exhaust gases to escape, as well as to control the sound output of the engine by using the muffler. Carmakers place a muffler and the tailpipe at the back of the car so that exhaust gases and sound can escape away from the driver.
The exhaust pipe seems like a very simple device, but it can still greatly affect the car’s performance and emissions output. For example, if there’s a leak in the exhaust pipes, it can affect the engine performance.
Worse still, if the leak is at the front pipe, it will allow very harmful gases to escape into the atmosphere since it hasn’t been filtered by the catalytic converter.
Emissions System Problem Signs To Look Out For
The signs and symptoms can differ depending on which device in the system is not working properly. However, here are the general signs you should look out for:
1. Performance Loss
Since many emissions systems work in conjunction with the engine’s intake system, it can affect your car’s performance if one of them is faulty.
For example, the secondary air injection system monitors the amount of hydrocarbon gases coming out of the engine. If it gets the wrong reading, it can trigger the Engine Control Unit (ECU) to do something that it’s not supposed to (such as introducing more air than necessary) that can affect performance.
Other components can also cause performance loss. For example, an EGR that’s stuck open may introduce too much exhaust gases. This makes the engine starve for oxygen, which can affect performance.
Another example is when you have a bad catalytic converter (which you can diagnose further by figuring out how to tell if catalytic converter is bad). Over time, catalytic converters can become dirty and clog up. When this happens, back pressure will build up which slows down exhaust gas flows. If there’s too much back pressure, the engine’s performance will suffer.
Performance problems can manifest in different ways, such as rough idling, misfires, or stalling out of nowhere. Of course, there are many causes for engine performance loss. To verify if it’s an emissions system, check if you have these other symptoms:
2. Increased Fuel Consumption
In addition to performance loss, your engine may end up using more fuel if you have an emissions system problem. This usually happens when the EVAP system isn’t working properly and allowing fuel vapors to escape rather than recirculating them.
As a result, your engine uses more fuel to keep it running since the fuel vapors aren’t helping with the combustion.
3. Fuel Or Exhaust Gas Smell
If you smell fuel whilst in the car, then this is a sign that your EVAP system isn’t working properly. Rather than recirculating them, the system is allowing fuel vapors to escape. Leading to the smell of gas in the car (and figuring out how to get gasoline out of clothes).
Keep in mind that the smell of fuel may indicate a different problem. You may have a leak in the fuel tank, pump, or one of the lines. It can also be a sign that there’s a leak in the fuel injectors, or that one of the spark plugs is loose.
Meanwhile, an exhaust smell usually means there’s a leak in the exhaust system. This usually happens when there’s damage from road debris to one of the pipes. It can also happen when there’s excess corrosion on one of the exhaust pipe components, which results in a hole that allows the exhaust gases to escape.
Either way, the smell of fuel or exhausts gases is not something to be taken lightly when you’re driving. Both are very harmful to your health and can lead to serious lung and other health problems in the long run.
Additionally, in the case of a fuel leak, it can result in a fire. Fuel vapors are still highly combustible. If you smell either of them while driving, you should immediately take your car to a repair shop. Diagnose the problem and repair them as soon as possible.
4. Your Car Fails An Emission Test
The most obvious sign is when your car fails to pass an emissions test. Every car is designed to meet emission regulations, otherwise, carmakers wouldn’t be allowed to sell them. So, if your car is in top condition, it should easily pass the test.
If it fails the test, then there’s a problem with one or more of the emissions systems. It may be because of a clogged catalytic converter that isn’t filtering out harmful gases properly. Or it could also be because of a faulty EGR valve that isn’t opening which causes your engine to produce more NOx gases.
Finding the cause may prove to be difficult. However, the good news is that an emissions system problem will often trigger a check engine light. This means you can then scan your car’s On-Board Diagnostics (OBD) system to find out the cause.
Troubleshooting Emissions System Problem
In some cases, you may need to physically inspect your emissions systems to find out the cause. But if your check engine light is on, you can scan the car’s OBD system to help find the exact cause.
A bit of explanation: the OBD system is a diagnostic device that registers error codes when something isn’t working properly in the car. If the car’s ECU detects an anomaly and can’t fix the problem on its own, it will register an error code that triggers the check engine light.
If the light is on, you can scan the OBD system by using an OBD scanner to see what triggered the check engine light. Keep in mind that cars before 1996 uses the OBD-1 system, which is different than the modern-day OBD-2 system.
Using the OBD scanner is fairly straightforward: you connect it to the car’s OBD port and then turn it on. It may require you to input your car’s make, model, and VIN. Afterward, choose to scan the system and it will return engine codes.
Expensive scanners will be able to tell you what these codes mean, but if you don’t have them, you can write them down and check them in the owner’s manual or the internet to see what they mean.
We already wrote in great detail about how to use an OBD scanner, and you can learn more here. Now, let’s take a look at the common error codes that are related to the emissions system:
Emissions System Problem: Common Error Codes And What They Mean
There are literally thousands of error codes that your car can register. Here are the common error codes that are related to the emissions system and a quick explanation of what they mean:
- P0401 – EGR Flow Insufficient. This means either the valve or the vacuum line is clogged and requires cleaning or a replacement.
- P0411 – EVAP System Control Incorrect Purge Flow. Requires an air pump, vacuum hose, or solenoid replacement. However, might also be a wiring harness issue.
- P0420 & P0430 – Catalyst System Low Efficiency (Bank 2 for P0430). This essentially indicates a problem with the catalytic converter. Sometimes a faulty oxygen sensor can cause this, but it commonly means you need to replace the catalytic converter.
- PO440, P0442 (just like the P0442 code Chevy Silverado), P0466, and P0455 – EVAP System. A loose fuel cap may cause this, but can also mean a leak in the EVAP system.
Those are the codes that are directly related to the emissions system devices. However, keep a lookout for P0133 and P0135 codes. These codes mean there’s a problem with your oxygen (O2) sensor.
The O2 sensor monitors the amount of oxygen in the exhaust gases. A faulty sensor may give wrong readings which can trigger the ECU to put more fuel into the engine than necessary. As a result, the exhaust gases become more toxic and can be the reason why your car didn’t pass the emission test.
Emissions System Problem Repair Costs
So, now you know the signs and how to diagnose an emissions system problem. The next question is how do you repair them and how much will it cost you? Since there are different devices, the repair costs will depend on which device you need to fix and what needs to be done.
Some devices can be cleaned, such as the EGR valve and catalytic converter. Others such as the PCV system will need to be replaced altogether. Here are the general estimates for each of them (as well as how much is a catalytic converter):
- PCV Replacement Cost: $80 – $120
- EGR Replacement Cost: $250 – $350
- EVAP System Replacement Cost: $260 – $640
- Secondary Air Injection System: $270 – $390
- Catalytic Converter Replacement: $900 – $2,500
- Exhaust Pipe Repairs: $100 – $700
Keep in mind that these are just estimates. The final cost will depend heavily on your car’s make and model. We’ve linked each estimate to articles that have more details on the repairs and you should find them helpful.
As you can see, the catalytic converter is the most expensive one to replace. As mentioned, they’re made out of very expensive precious metals (you can learn more in our guide on what are catalytic converters made of). The good news is that you may be able to clean your catalytic converter to solve the problem. But if the problem persists, or it’s already 10 years old, then it’s time to replace your catalytic converter.
Emissions System Problem: Questions & Answers
Got any more questions regarding your car’s emissions system? The answer you’re looking for might be below:
Can I Drive With An Emissions System Problem?
Technically, you can, but you shouldn’t. While chances are the car can still operate, you will still see a significant drop in performance and efficiency. Additionally, some problems may put you at significant health and safety risks.
Can I Drive Without A Catalytic Converter?
The car will still operate, but removing a catalytic converter is against the law. You will face fines of up to $250.
When Do I Have To Do An Emissions Test?
This depends on what state you’re in. Some states like New York will require you to do it every 12 months. While others such as California require it every two years. Check your local DMV’s website to find out.
Where Can I Do An Emissions Test And How Much Will It Cost?
A lot of auto repair shops, especially national chains, are certified to do an emissions test. This includes Pep Boys, Jiffy Lube, and AAA. We recommend inquiring first to your nearest outlet though before you visit them.
As for the cost, it will typically cost around $25 – $50 to do an emissions test.
Can I Do Emissions System Problem Repairs Myself?
In many cases, you can. A lot of the repairs are not quite as difficult as it seems. We recommend checking the links that we’ve provided in the repair cost section. If it doesn’t seem to be too difficult, doing the repairs yourself is a great way to save money.
Emissions System Problem: Wrap Up
So, to summarize, your car’s emissions system consists of six different devices. The PCV valve, the EGR system, the EVAP system, the secondary air injection system, the catalytic converter, and the exhaust pipes.
Modern cars now have these systems, with EGR and secondary air injection systems being the exception and may not be present in some cars if the carmaker doesn’t deem it necessary.
An emissions system problem can occur over time as the parts age and wear down. When they do, you may experience performance and fuel consumption issues. And the car will definitely struggle to meet emissions regulations.
We recommend fixing an emissions system problem as soon as possible. Neglecting the problem can cause further issues with the car, not to mention it will harm the environment and your car will struggle to pass its emissions testing.