Whether you’re new to car tinkering or just searching for a bit more information, the ultimate EGR valve guide will provide some much-needed insight into the car component.
REDUCING EMISSIONS
To combat the ever-feared greenhouse gas emissions from road transport, vehicles have been fitted with numerous tools to help reduce emissions. One tool you’re likely to find in your car is an Exhaust Gas Recirculation system or EGR.
An EGR valve is designed to control the nitrogen oxide emissions produced during the engine’s combustion process. Nitrogen oxide is formed when oxygen and nitrogen from gathered air merge with fuel as it is ignited within the combustion chamber. This causes the temperature to rise significantly, producing high NOx emissions. Using an EGR system, a small portion of exhaust gas is returned to the engine’s combustion chamber, lowering the temperatures and reducing NOx production.
Reducing NOx emissions is very important as NOx is a crucial component in smog, negatively affecting both humans and the environment. The EGR has become a significant tool in battling the creation of harmful emissions and has been incorporated into the majority of modern cars.
HOW DOES IT WORK?
As stated earlier, an EGR system’s job is to recycle small portions of exhaust gas combined with fresh air. By doing this, the amount of oxygen used is lowered, and water vapour content in the combustion mix is increased, reducing the highest temperature reached. Once the engine is on, the EGR valve activates and syncs up to the vehicle operating temperature as speed increases. The EGR valve regulates the flow of exhaust gasses, and once the journey is complete, it will resume its closed position and stop the escape of exhaust gasses.
DIFFERENT TYPES OF EGR VALVES
EGR valves come in different types depending on the make and model of the vehicle. Newer vehicles will most likely be fitted with a Digital EGR valve operated electronically. Older vehicles tend to be fitted with vacuum-operated EGR valves. Below is a list that briefly describes the common types of EGR valves:
Diesel high-pressure EGR valve:
This EGR valve will divert high-flow, high-soot gas before entering the DPF. The gas is then returned to the inlet manifold through a pipe or drillings in the cylinder head. A vacuum is created in the inlet by a second valve.
Diesel Low-pressure EGR valves:
Unlike high-pressure EGRs, this EGR valve diverts exhaust gas after it has gone through the DPF. The gas flows at lower levels, but the soot is bare present within the gas itself. The gas is then passed back to the inlet manifold using a pipe.
Gasoline EGR valves:
These types of EGR valves are similar to the high-pressure variant. The vacuum is created via cylinder depression, which pulls the gases in. The flow of gas is controlled by the opening and closing mechanism of the EGR valve.
Vacuum-operated EGR valves:
These EGR valves use a vacuum solenoid to adjust the vacuum to the diaphragm to open and close the EGR. These types of EGR valves are customarily equipped with sensors that inform the engine control unit (ECU) of the valve’s current position.
Digital EGR valves:
These are the most recent types of EGR valves. They use a solenoid or stepper motor and are fitted with a sensor. Digital EGR valves respond directly to signals sent from the ECU and regulate exhaust gas flow accordingly.
PROBLEMS WITH EGR VALVES
A common issue amongst cars with EGR valves is the valve sticking due to carbon deposits in the system. Worst-case scenarios can even seem both EGR passage and the valve blocked utterly, preventing gas recirculation attempts. There are many signs that your EGR valve is blocked, but the most common is black smoke visually coming out of the exhaust pipe. The smell of fuel is another potential indicator that your EGR valve is having problems. You may also notice an increased fuel usage as well as the reduced performance of your car. There are also times when an increased rate of knocking noise can be heard from the engine. If the EGR valve is faulty, it will neither open nor close and then the Engine maintenance light will appear on your dashboard. Once blocked, you will notice more extreme symptoms, such as a complete engine shutdown and intense overheating.
EGR VALVE FAULT CODES
Faulty EGR Valves can be diagnosed with the appropriate fault codes.
P0401: Insufficient flow within the EGR Valve
P0402: Excessive flow within the EGR Valve
P0403: EGR Circuit failure
P0404: Poor performance with the EGR circuit
CAN I DRIVE MY CAR WITHOUT AN EGR VALVE?
Due to Euro 6 Emissions Standards, cars and compliant vehicles must have their EGR attached to pass their MOT. This means it is illegal to remove your EGR valve as well as your Diesel Particle Filter, and you could end up paying a sum of up to £1000 in fines.
WHEN TO REPLACE A FAULTY EGR VALVE
An EGR valve not operating efficiently should be replaced as soon as the problem is noticed. Left too long and a faulty EGR valve can lead to dire consequences for your vehicle. Like the DPF system, this should be done by a certified mechanic to avoid causing more problems. The mechanic will perform the necessary steps to make your car fitted with a new, appropriate EGR valve. Sometimes, you may not even need a new EGR valve and can go through with an EGR valve cleaning process instead. This effectively clears a blockage in the EGR valve before it becomes a significant issue.
ABOUT DPF RESTORE
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