Effects of Dirty EGR Valve on Common-Rail Diesel Engines – We will talk about one of the important parts of a common rail diesel engine, namely the EGR valve. This valve is very annoying if we do not take good care of it. On the other hand, this valve reduces NOx from the rest of the combustion in the combustion chamber which is very dangerous for humans.
Before talking about the problems that will occur if the EGR valve is dirty, we will first discuss how it works. Adding knowledge is obvious, but more importantly, it will help you understand the effect of a dirty EGR valve on common rail diesel engines.
Read more: How to Clean a Honda Car EGR Valve
How Does the EGR Valve Work on Common Rail?
The EGR valve provides a controlled reduction of oxygen content in the combustion process. You do this by entering the inert exhaust gas into the air/refueling into the cylinder in the intake manifold. This causes a slower explosion in the cylinder and lowers the combustion temperature and pressure. Because NOx (Nitrogen Oxide) is harmful, it is possible to reduce the NOx concentrate that escapes into the air. Engines in high-temperature conditions will produce more NOx.
For the recirculation of exhaust gases back to the intake manifold, there is a small path between the intake and exhaust manifolds. This is where the Exhaust Gas Recirculation (EGR) Valve is located. It adjusts the amount of exhaust gas that is recirculated back to the intake manifold. The vacuum intake in the intake manifold sucks exhaust gases back into the engine. But the amount of recirculation must be strictly controlled. Otherwise, it can have the same effect on engine performance, idle quality, and driveability as a large vacuum leak.
With EGR, the amount of exhaust gas that returns to the intake manifold is only about 5 to 10% of the total exhaust gas. But it is sufficient to dilute the air/fuel mixture to have a cooling effect on the combustion temperature of the engine. The EGR valve is only active at a stage of operation which varies with the particular vehicle. This keeps the combustion temperature below 1500 degrees Celsius to reduce the reaction between nitrogen and oxygen that forms NOx.
When the engine is idle, the system will close the EGR Valve and there is no flow of Exhaust Gas Return to the intake manifold. The EGR Valve remains closed until the engine has finished warming up and is operating under load. When load and combustion temperatures increase, the system opens the EGR Valve and begins sending exhaust gases back to the intake manifold.
Most EGR systems on older cars use a vacuum-regulated EGR valve. While newer vehicles tend to have an electronic EGR valve to control exhaust gas recirculation.
Effects of Dirty EGR Valve on Common-Rail Diesel Engines
Some common-rail diesel engines have an EGR or Exhaust Gas Recirculation Valve. The EGR valve functions to drain some of the remaining combustion gases (NOx) back to the intake manifold. This results in lower exhaust emissions. In addition, it also helps get a better air supply response.
Well, the condition of the EGR valve needs to be considered. If you often use low-quality fuel, the remaining carbon in the form of combustion can make the EGR valve dirty. The impact, of course, can make engine performance decrease and exhaust gas emissions to be high.
To avoid that, I highly recommend cleaning the EGR valve at least once a year. Or you can calculate based on vehicle mileage, which is once every 10 thousand km. If you routinely carry out regular maintenance, the EGR is very rarely found to be damaged. The damage that often occurs is in the electrical or the EGR valve sensor.
Symptoms of Bad EGR Valve (Include Effects of Dirty EGR Valve on Common-Rail)
Symptoms of a faulty or malfunctioning EGR valve include:
- rough engine idle or stalling.
- the smell of fuel.
- increased fuel consumption aka wasteful.
- ping, tapping sound.
- failed smog test.
- The engine indicator light is on.
EGR Valve Holds in Closed vs Open Position
There are actually two types of problematic EGR valves, with different symptoms of course. The EGR valve can fail to function in two ways: It can open continuously, or it can be closed continuously.
If the EGR Valve is Retained in the Open Condition:
This kind of condition will cause a continuous flow of exhaust gases to the intake manifold. You will notice one or more of the following symptoms:
- Rough idle when starting the engine (i.e., when the engine is cold) and sometimes at a red light on the road or when looking for a place in the parking lot (i.e., at low engine speed while the engine is warming up).
- Stalling (skinny) when the engine is idle.
- Increased fuel consumption (aka wasteful).
- A slight or strong smell of fuel when operating the vehicle, due to increased hydrocarbons leaving the exhaust.
- Your car failed the emission test. When the engine is running at low RPM, the lower temperature in the combustion chamber prevents all of the fuel from burning. So that the flow of unburned hydrocarbon gas out of the exhaust increases significantly.
- The Check Engine Lamp (or Malfunction Indicator Light, MIL, depending on your car model) lights up on your dashboard.
If EGR Valve Holds Closed (Effects of Dirty EGR Valve on Common-Rail):
This condition will permanently block the flow of exhaust gases into the intake manifold. You will notice one or more of the following symptoms:
- A ping or tapping sound comes from the engine at low RPM (at a speed higher than idle). Noise occurs when the car starts the initial fuel when it meets high temperatures.
- Hard blasting. A second ignition can occur after normal ignition, and the two can combine with enough power to cause engine damage.
- Your car failed the emission test. The high temperature in the combustion chamber allows the formation of excess nitrogen oxides, which is released through the exhaust pipe.
- The Check Engine light, or Malfunction Indicator Light (MIL), lights up on your dashboard.
Troubleshooting: Is it an EGR Valve or Something else?
To make matters more complicated, the same engine performance issues that indicate a bad EGR valve can also indicate problems in other parts of the system:
- spark plug,
- spark plug wire,
- fuel filter,
- fuel pump regulator,
- and various engine sensors.
The increase in hydrocarbon emissions is not always caused by a stuck-open EGR valve. Problems in other systems can cause the same symptoms as well. Examples are leaking fuel injectors, poor ignition timing, poor cylinder compression, poor oxygen sensor, or other problems.
Read more: Supply Pump Common Rail Diesel Engine Works
Similarly, increased NOx can be caused by a vacuum leak, clogged fuel injector, low fuel pressure, leaky head gasket, or other problems.
Rough idle can be caused by a faulty ignition coil, a vacuum leak, or an ignition system problem.
So before spending money and replacing parts, troubleshoot the EGR valve and other system components to try to narrow down the problem.
If your car has an electronic EGR valve, troubleshooting will be easier. Because it will have the MIL on the dashboard, you will be able to tell what engine system malfunction triggered the indicator light to come on. With aftermarket scan tools, you can pull trouble codes from the computer’s memory and see what system or component is causing the problem. Then, you can try to find the fault with the help of the vehicle repair manual for the make and model of your car.