Symptoms of Faulty EGR Valve on Diesel – Is your car’s EGR or Exhaust Gas Recirculation valve (your Exhaust Gas Recirculation valve) damaged? Maybe not. I will tell you the symptoms below. But before you start replacing components, remember that the same engine performance issues that indicate a bad EGR valve can also indicate problems in other parts of the system. If you don’t do the troubleshooting, you may end up replacing unnecessary parts and wasting time and of course money. Let’s get started.
Read more: How to Clean a Honda Car EGR Valve
So this article will tell you a few things:
- symptoms of poor EGR valve;
- how to start investigating if the problem is your EGR valve or something else;
- what is an EGR valve and how does it work;
- and various types of EGR valves.
Symptoms of Faulty EGR Valve on Diesel
Symptoms of a faulty or malfunctioning EGR valve include:
- rough engine idle or stalling
- smell of fuel
- increased fuel consumption aka wasteful
- ping, tapping sound
- failed smog test
- 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.
Read more: Purpose of Diesel Engine Common Rail System
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 occasionally at a red light on the road or when looking for a parking space (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:
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.
- Loud 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.
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, and 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.
EGR Valve Work: Processing Exhaust Gas
The outside air drawn in through the engine’s intake manifold contains nearly 80 percent nitrogen and 20 percent oxygen, along with small amounts of other elements. When the outside air combines with the fuel and ignites in the combustion chamber, temperatures can reach above 2500o F (or 1370o C). Combustion at this temperature burns the normally inert gas nitrogen, creating nitrogen oxide (NOx) gas, which causes air pollution and human health problems.
However, when the burnt exhaust gases are fed back into the combustion chamber through the EGR valve, the temperature decreases, inhibiting the formation of NOx gas.
What the EGR Valve Does
The EGR valve is a small component designed to allow the flow of exhaust gases to the intake manifold in a controlled amount. As such, it is a simple valve that closes and opens as needed.
The EGR valve has one single job to do, regardless of system configuration, type of control, and a number of sensors: namely, either to open and direct exhaust gases into the combustion chamber, or to close and prevent them from entering.
Every time you start the engine, the valves come on and wait in the closed position, blocking the flow of exhaust gases.
Once the engine reaches operating temperature and the speed increases, the valves — either via vacuum or electronic control — gradually open, allowing the combustion exhaust gases to enter and join the air-fuel mixture in the combustion chamber. If you slow down enough or stop, the valve gradually closes and blocks the flow of exhaust gases. And the process continues as long as the machine is running.
After you turn off the engine, the EGR valve closes and stays in that position.
EGR Valve System Type
Gasoline and diesel-powered engines on the road today can use one of several different EGR valve configurations.
On older vehicle models, you’ll recognize the EGR valve as a round, thick metal disc about three inches in diameter, usually toward the top of the engine and on the sides. On these older models, a small diameter vacuum hose operates the basic EGR valve. The hose connects the top of the valve to the throttle body or carburetor. The metal disc of this valve has a vacuum diaphragm, spring, and plunger.
Later models were equipped with a vacuum electronic EGR valve in a small block or cylinder. The valves work the same way as on older models, except that the electronic EGR position sensor communicates with the car’s computer for better control. You may see an electrical solenoid connected through the vacuum line to the valve as well.
Newer vehicle models use an electronic EGR system which may include additional components, even a digital valve which eliminates the need for vacuum control altogether.
A more radical design, implemented in some models, is the replacement of the valve with an EGR jet at the bottom of the intake manifold.
Some newer high-efficiency engines, for example, those with variable valve timing (VVT), do not even use the EGR system.
EGR Valve Type
- Vacuum controlled EGR valve
- Backpressure EGR valve
- Electronic vacuum controlled EGR valve
- Digital EGR Valve
- EGR jet (replaces EGR valve).
Finding EGR on Corvettes and on Trucks
Symptoms of a bad EGR vary and resemble problems with other engine systems. But now that you know the types of symptoms a problematic EGR valve will produce, include them in your troubleshooting test. And refrain from swapping components that try to fix the problem before knowing which part is causing you problems. You will only waste time and money unnecessarily. Troubleshoot your EGR valve and other components.