What is Exhaust Gas Recirculation or EGR?
Exhaust Gas Recirculation or EGR is the car part that helps reduce emissions by recirculating gases through the intake to help lower the combustion temperature. This process helps reduce nitrogen dioxide emissions NOx.
The first EGR valves made were electro-pneumatically operated. This type of drive had the advantage of isolating the electronic part of the EGR from the high-temperature components. Modern engines with EGR systems are almost entirely equipped with electrically operated valves and controlled directly by the electronic engine control unit.
The advantage of EGR valves with DC electric motor, compared to those with electro-pneumatic drive, is the shorter response time. For these valves, the opening and closing can be performed within 100 milliseconds. This is important because the EGR valve is completely closed when the driver wants the maximum torque.
How does the EGR valve work?
The EGR is a system that allows the reintroduction of the gases resulting from combustion back into the intake manifold. This process leads to a significant reduction of NOx emissions because it reduces the two elements that underlie its production.
By reintroducing the flue gas into the intake, some of the oxygen required for combustion is replaced by flue gas, which leads to a decrease in excess oxygen. On the other hand, because the flue gas absorbs some of the heat generated by the combustion, the maximum temperature per cycle is reduced.
A computer that runs a solenoid in sequential masses is responsible for the good functioning of the EGR valve. If the valve is controlled very much by the injection computer, the pressure created by the vacuum pump acts on the EGR valve and opens it.
This process of exhaust gas recirculation eventually leads to the accumulation of carbon and calamine particles inside the intake. If the measures are not taken in time, the carbon and calamine particles cling to the engine parts and no longer allow them to function in optimal parameters.
So you will have to change the EGR valve. One solution that you may have heard very often in the automotive world is engine decarbonization, but I do not like this solution very much because I have not seen results and I will explain why in a future article. If you do not consider decarbonization before changing to the EGR valve, it seems that you will have to go to a service for a check and change.
Can petrol engines have EGR?
Because most petrol engines work with the stoichiometric mixture, NOx emissions are relatively low and no EGR system is required. An exception to this rule is made by direct injection petrol engines, which due to the stratified mixing mode may require the use of the EGR.
How can an EGR valve get stuck?
It can be stuck in the closed or open position. Neither one is recommended, but here are the consequences depending on the situation.
What problems can a stuck EGR valve cause to the car?
If it’s stuck in the open position:
- The engine becomes saturated in a very short time.
- The acceleration power will drop dramatically, and the engine may stop at idle or while driving.
- Turbocharger problems. If the EGR remains open and the exhaust gases do not cool, the result is as clear as possible, namely that the exhaust gases will not cool. Once the engine overheats, the engine oil breaks down and takes the turbocharger path, and for this reason, the turbocharger suffers, failing to function.
- Engine problems. If too much overheating of the engine is reached, the lubrication will be consumed permanently, which means that the engine instead of consuming fuel, it will consume its own oil, which is why the engine will disintegrate, and in this situation, a new engine will be needed.
If it is stuck in the closed position:
- The valve will no longer have the power to operate. It’s like as if you were canceling an engine component.
- Nitrogen oxide emissions will exceed the limit allowed by law – this will be observed with the naked eye as the smoke becomes darker and denser.
- Another symptom of the car that I noticed is that the engine is louder.
What can I do if the EGR valve is stuck?
As I said before, go to service, diagnosis, change the EGR if needed, or the other solution, try cleaning it, this could be the simplest solution. The EGR valve differs in price from model to model and from brand to brand.
Correct diagnosis of EGR problems
The EGR, being a system for reducing nitrogen oxide emissions, is monitored by the injection computer in order to detect possible defects. Because it is a pollution abatement system, when an EGR defect is detected, the Check Engine light will lit.
The diagnosis of the EGR system consists of the monitoring of the electronic elements that belong to it:
- EGR valve (2)
- Exhaust Gas Recirculation Cooling Valve (3)
- Throttle on intake manifold (6)
- cooled gas temperature sensor (5)
- The flow control system for recirculated gases – EGR
The flow control system for recirculated gases – EGR
- EGR valve
- Exhaust Gas Recirculation Cooling Valve (by-pass valve)
- radiator for flue gas cooling
- temperature sensor
- injection computer
EGR Valve diagnosis
Adjusting the position of the EGR valve is particularly important because it affects the engine torque and the level of pollutant emissions. For this reason, most EGR valves are equipped with a position sensor that transmits the information to the injection computer.
As I said earlier due to particle deposition EGR valves can block. Depending on the position, locking an EGR valve can impact engine integrity or pollutant emissions. Thus, if the EGR valve is blocked in the closed position, the flue gas will no longer enter the intake manifold and the nitrogen oxide emissions will increase.
On the other hand, if the EGR valve blocks in the open position the flue gases will be recirculated all the time in the inlet and can affect the safe operation of the engine due to the high temperature.
OBD error codes for a faulty EGR valve
- P0400 – Exhaust Gas Recirculation Flow Malfunction
- P0401 – Exhaust Gas Recirculation Insufficient Flow
- P0402 – Exhaust Gas Recirculation Excessive Flow
- P0403 – EGR Control Circuit
- P0404 – EGR Control Circuit – signal outside limits
- P0405 – EGR Sensor “A” Circuit – signal below the minimum limit
- P0406 – EGR Sensor “A” Circuit – signal above the minimum limit
- P0407 – EGR Sensor “B” Circuit – signal below the minimum limit
- P0408 – EGR Sensor “B” Circuit – signal above the minimum limit
- P0405 – EGR Sensor “A” Circuit
- P0486 – EGR Sensor “B” Circuit
- P0489 – EGR Sensor “A” Control Circuit – signal below the minimum limit
- P0490 – EGR Sensor “B” Control Circuit – signal below the minimum limit
- P2413 – Performance of exhaust gas recirculation system – below the limit
Exhaust Gas Recirculation Cooling Valve diagnosis
One of the reasons why EGR systems are used is to reduce the combustion temperature in the cylinder. The flue gases, if directly introduced into the exhaust manifold, due to the high temperature, have no significant effect on the process of reducing nitrogen oxide emissions.
Since 2001, most diesel engines for cars have been equipped with EGR cooled systems. These systems use a radiator circuit for cooling exhaust gases before they are introduced into the engine. For the cooling of the flue gases, the engine coolant is usually used.
By cooling, the density of the gas is increased and the efficiency of the EGR system is improved for two reasons:
- the combustion temperature in the cylinder decreases
- the amount of oxygen in the fresh gas decreases due to the higher density of the flue gas
The flue gas cooling is not continuous but only after the engine temperature reaches a certain limit. The cooling circuit is provided with a bypass valve that allows the flue gas to pass through the radiator or bypass it.
OBD error codes for the EGR cooling Valve
- P2425 – Exhaust Gas Recirculation Cooling Valve Control Circuit / Open
- P2426 – Exhaust Gas Recirculation Cooling Valve Control Circuit – signal below the minimum limit
- P2427 – Exhaust Gas Recirculation Cooling Valve Control Circuit – signal above the minimum limit
- P2457 Exhaust Gas Recirculation Cooling System LOW Performance
- P245A Exhaust Gas Recirculation Cooler Bypass Control Circuit / Open
- P245B Exhaust Gas Recirculation Cooler Bypass Control Circuit Range / Performance – signal outside limits
- P245C Exhaust Gas Recirculation Cooler Bypass Control Circuit Low
- P245D Exhaust Gas Recirculation Cooler Bypass Control Circuit High
The decision to cool the flue gas is made by the injection computer based on the information received from the temperature sensor. It reads the temperature of the exhaust gases before they are introduced into the intake manifold.
EGR temperature sensor OBD error codes
- P040A EGR Temp Sensor Circuit
- P040B EGR Temp Sensor Circuit Range – signal outside limits
- P040C EGR Temp Sensor A Circuit Low
- P040D EGR Temp Sensor A Circuit High
- P040E EGR Temp Sensor Circuit Intermittent
- P040F EGR Temperature Sensor discrepancy between ‘A’ and ‘B’ sensor signals
- P041A EGR Temp Sensor B Circuit
- P041B EGR Temp Sensor B Circuit signal outside the range
- P041C EGR Temp Sensor B Circuit Low
- P041D EGR Temp Sensor B Circuit High
- P041E EGR Temp Sensor B Intermittent Circuit
The control of the flue gas flow can only be done by opening / closing the EGR valve or with the help of the throttle from the intake manifold. The shutter has a constructive form similar to that of a throttle used on gasoline engines but is used for a different purpose.
When a high flue gas flow is desired in the intake manifold, the throttle closes, the fresh airflow is restricted and the exhaust gas flow increased.
OBD codes for the throttle
- P0487 EGR Throttle Control Circuit A Open
- P0488 EGR Throttle Position Control Range / Performance
- P213A EGR Throttle Control Circuit B Open
- P213B EGR Throttle Position Control Circuit B Range / Performance
- P213C EGR Throttle Position Control Circuit B Low
- P213D EGR Throttle Position Control Circuit B High
- P2141 EGR Throttle Position Control Circuit A Low
- P2142 EGR Throttle Position Control Circuit A Low
How to clean an EGR valve?
There are high chances that an EGR valve has been broken, and then repaired to function properly, but most often it is more cost-effective to purchase a new valve than to repair the broken one.
Older EGR valves are simpler and easier to repair because they are vacuum controlled and the repair procedure is as simple as possible. If your machine has a vacuum controlled EGR valve, only the inner membrane can be replaced, and it can be cleaned to behave like a new EGR valve.
When discussing the EGR valves of the new generation machines, it should be noted that they have different electrical components, so they are difficult to repair even by the best experts.
For this reason, and in this case, the most suitable solution is the choice of new EGR valves.
There are also newer generation cars, which have electric motors and have EGR, but the arc valve. These can be stuck and can result in cleaning and lubrication of the shaft, which will destroy them.
In case you have the idea of cleaning the EGR valve, in the first phase, it is necessary to remove the curvature using a knife, after which you have to clean it several times using a specially designed brake cleaning device.
After you also deal with this stage, it will be necessary to lubricate the valve using the WD-40, because in this way you will be able to make sure that the parts move properly.
If the idea of changing the EGR valve seems to be more convenient, you should consider that if the EGR valve of your car is electronic, you must necessarily use the OBD2 scanner to remove the problematic codes after replacement.
Using this scanner is also necessary to make it a basic setting for the new EGR valve. If you do not return the ideal parameters of the new EGR valve, you may later encounter the same error code, and thus more than likely you will arrive with the car in service.
Once you have come to the conclusion that the EGR valve is bad, you must definitely repair it, so you can go to the service, for the specialists to deal with this unpleasant situation.
If you do not like the idea of going to the car in service to replace this component, you should consider the following steps, first of all, to clean the EGR valve, and then to remove the jams and see if the valve operating mode is correct.
- Therefore, it is necessary to disconnect the car battery, after which you must disconnect the sensors and the clamps, and then you must loosen the screws that hold the EGR valve.
- Once you have completed all these steps, you will need to use a specially designed EGR device to clean the hoses and valves.
- After you finish cleaning the hoses and valves, you will need to reconnect the car battery. It is extremely important that you do not allow the special cleaning agent to reach one of the electrical components of the machine.
- However, to clean certain electrical components, it would be advisable to use a special electrical device created for this purpose.
- If you have not yet gone through such a process with your personal car, our recommendation is to take your car in service for the specialists to deal with this aspect.
- Depending on the car service chosen, but also depending on the make and model of the car, and not least on the basis of its age, you will be able to pay more or less for this intervention.
How to detect a failing EGR valve?
The procedure required to detect a bad EGR valve is highly dependent on the EGR valve that the car has. If you follow the steps below, you will personally fix the problem.
- If you want to test an electronic EGR valve for a vacuum controlled EGR, first of all, you need to check the vacuum hose between the inlet and the EGR.
- You need to have a vacuum pump handy to use in order to open the EGR valve and to see if the pressure is maintained.
- If it is not under pressure, it is necessary to change the membrane if you have this possibility, or if not, to change the whole EGR unit.
- It is also necessary to remove the EGR valve and find out if it opens when you operate the vacuum pump. If the EGR valve behaves normally, it is necessary to check the solenoid, whose role is to control the EGR valve, and also here it is necessary to check the power and the presence of the grounding.
EGR controlled electronic system
- First of all, you need to remove the EGR valve unit to see what the valve opening and closing is. Then, you need to connect a car battery charger when you are diagnosing, to find out if the voltage in the car is good when the diagnosis occurs.
- The next step is to open and close the EGR valve using the OBD2 scanner. This procedure must be performed several times to verify the function.
- Then, it is necessary to make a basic setting and to reset the saved parameter, with the scanner. It is also necessary to check all the problems regarding the EGR wiring.
- After that, you must open the EGR valve and see if there is water inside the valve, or if there is corrosion infiltration, and you must use an electrical cleaning device to clean the EGR valve if you find that there is corrosion.
- Then reinstall the EGR valve and try again this entire process, but if the EGR valve is defective, then you need to replace it with a new one.
How much does an EGR cost?
Depending on the make and model of the car, the cost of an EGR valve can range from $ 55 to $ 300, while labor can cost anywhere from $ 20 to $ 60.
Older cars are equipped with vacuum-controlled EGR valves, so drivers who own such cars can feel lucky because if necessary, they will spend less money.
Newer cars, however, have an EGR cooler integrated with the EGR valve, so you can not just replace the EGR valve but also the EGR cooler, and the Volkswagen cars are an example in this case.
If, for example, an old car needs a new EGR valve, the price for it may be less than $ 90. For newer cars, however, the prices are higher.
Best EGR Valve Cleaners
featured image by Towel401, distributed under a CC-BY 2.0 license.