Within modern, diesel combustion engines, Exhaust Gas Recirculation (EGR) is a method to manage Nitrogen Oxides (NOx) emissions, produced as a byproduct during the combustion process. Air from the environment is usually a mix of Oxygen and Nitrogen. When the air combines with fuel and ignites inside the combustion chamber, temperatures increase and produce NOx emissions.
The EGR system works by returning a little portion of an engine’s exhaust gas to the engine’s combustion chambers through the manifold, lowering combustion temperatures and so reducing the number of NOx emitted.
The EGR valve is the main component of the EGR system and it’s normally closed. It connects the manifold to the manifold and is controlled by either a vacuum or a built-in electric step motor. The function of the EGR valve is to regulate the flow of exhaust gas being recirculated reckoning on the engine load.
Nitrogen Oxide (NOx):
Nitrogen oxides are emissions produced as a byproduct from the method of combustion, Nitrogen, and Oxygen gases within the air react during combustion, especially at high temperatures.
NOx is a major component of smog and might have detrimental effects on human health furthermore as ecosystems and crops. Therefore, incorporating EGR systems into the planning of a car is very important with regards to lowering harmful emissions to save lots of the environment and have a positive impact on human health.
EGR Valve and an MOT Test:
In the past, car owners attempted to get rid of EGR valves and Diesel Particulate Filters (DPFs) from their vehicles to avoid costly repairs. However, for Euro 6 Emissions Standards compliant vehicles it’s now been stated by the Department for Transportation that removing the EGR valve or PDF is unlawful because the vehicle will not be compliant with the road vehicle regulations.
How to Troubleshoot an EGR Value?
Troubleshooting an EGR Valve:
Given the various styles of EGR valves, it’s always best to follow the troubleshooting procedures detailed within the service manual, however, some general steps may help to pinpoint a diagnosis.
- Read any fault codes on electronically controlled EGR valves employing a diagnostic tool.
- Check that all vacuum lines and electrical connections are connected and positioned correctly.
- Use a vacuum gauge to test the vacuum supply hose for vacuum at 2000 to 2500 RPM. No vacuum at normal operating temperatures would suggest a loose hose, a blocked or faulty ported vacuum switch or solenoid, or a faulty vacuum amplifier/pump.
- Check the vacuum solenoid while the engine is running. On electronically controlled EGR valves, activate the solenoid with a scan tool and check the vacuum at end of the pipe. If the solenoid doesn’t open when energized, is stuck within the open or closed position, or contains a corroded electrical connection, loose wire, or bad ground, EGR operation are going to be affected. Identify the foundation cause before replacing it.
- If possible, check the movement of the valve stem at 1500 to 2000 RPM. The valve stem should move if the valve is functioning correctly – if not, and there’s a vacuum, there’s a fault.
- Apply vacuum on to the EGR valve using either a hand air pump or scan tool counting on the sort of EGR valve. If there’s no change in idle quality, then either the EGR valve is faulty or the passages are completely restricted. If the engine idles rough or stalls, the matter is being caused by a malfunctioning system.
- Remove the EGR valve and check for carbon build-up. Where possible, remove any carbon, being careful to not contaminate the diaphragm.
- Inspect the EGR passageway within the manifold for clogging and clean if required.
What to look out for in a failing EGR valve?
Looking in a failing EGR Valve:
The symptoms related to EGR valve failure are like those of the many other engine management components, and since of this EGR faults still, be a source of headaches for several technicians. However, there are some signs to seem out for:
- Check engine light: like most engine management components, a controversy with the EGR valve may trigger the check engine light.
- Engine performance issues: if the valve is stuck open the vehicle’s air-fuel ratio is going to be disrupted causing engine performance issues like reduced power, poor acceleration, and rough idle. it’s going to also produce turbo boost pressure leaks, causing the turbo to figure harder.
- Increased NOx emissions: when the EGR valve remains shut, the resultant high temperatures within the combustion chamber will leave plenty of unburned fuel within the exhaust, resulting in increased NOx emissions and reduced fuel efficiency.
- Engine knock: the upper temperatures and NOx can also lead to increased detonation or knock, heard as knocking noises within the engine.
The reason EGR valves fail:
EGR valves operate during a hostile environment so over time will experience wear and tear. However, the only biggest explanation for failure is that the buildup of carbon particles from the exhaust gases together with the EGR and intake system passages. Over time this may clog tubes, exhaust gas channels, and eventually the valve’s plunger mechanism, causing it to either stick open or close. Failures may be caused by a rupture or leak within the valve diaphragm.
What are the Types of EGR Valve?
Types of EGR Valve:
Although there are several styles of EGR valve — earlier systems use a vacuum-operated valve, while newer vehicles are electronically controlled — the most types may be broadly summarized as:
Diesel high-pressure EGR valves:
Divert the high-flow, high-soot exhaust gas before it enters the diesel particulate filter – the soot can combine with the oil vapor to make sludge. The gas is then passed back to the manifold either via a pipe or internal drillings within the plate. A secondary valve is additionally wont to help create a vacuum within the manifold as this is often not naturally present on diesel engines.
Diesel Low-pressure EGR valves:
Divert the exhaust gas after it’s older the diesel particulate filter — this gas includes a lower flow but is nearly completely clean of soot. The gas is then passed back to the manifold via a pipe.
Gasoline EGR valves:
Divert the exhaust gases, very similar to the high-pressure diesel equivalent. The vacuum created by cylinder depression draws the exhaust gases in, and also the flow is regulated by the opening and shutting of the EGR valve itself.
Vacuum operated EGR valves:
Use a vacuum solenoid to vary the vacuum to the diaphragm and, in turn, open and shut the EGR. Some valves also include a feedback sensor to tell the ECU of the valve’s position.
Digital EGR valves:
Feature a solenoid or stepper motor and, in most cases, a feedback sensor. These valves receive a pulse width modulated signal from the ECU, to manage exhaust gas flow.
How Does an EGR Valve Work?
The majority of contemporary diesel vehicles incorporate EGR valves into their design to scale back NOx emissions and so meet stringent emissions regulations. EGR systems recycle some of the exhaust gas into the combustion chamber, where it combines with fresh intake air.
This lowers the Oxygen content and increases the water vapor content to the combustion mixture which reduces peak combustion temperature. Because more NOx is formed as peak combustion temperature rises, the EGR valve effectively reduces the number of NOx produced by the engine.
The EGR valve begins working once the engine is started, attains the proper operating temperature, and speed increases. Gradually, the EGR valve regulates the flow of exhaust gases. Once you block and also the engine stops, the EGR valve will return to its closed position and stop the flow of exhaust gases.
Problems with an EGR Valve:
A frequent problem with the EGR valve is sticking thanks to a build-up of carbon deposits. In worst cases, the EGR valve and EGR passages are often completely blocked, preventing the method of recirculating the exhaust gases.
Clogged EGRs are often the reason behind black smoke escaping the exhaust, additionally to increased fuel consumption or reduced performance. If the EGR valve fails to open or close, the ‘check engine’ light will illuminate on the dashboard.
A fuel odor smelt from inside the vehicle is additionally an indication of a failing EGR valve as more hydrocarbons are going to be emitted through the exhaust because of the rise in fuel consumption. The smell is well noticeable thanks to its irritating nature because it can result in human health issues.
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