What Does the EGR Valve Do?
The Exhaust Gas Recirculation Valve (EGR) is fitted in modern gasoline and diesel engines to help fight the formation of Nitrous Oxide (NOx) and Sulphur Dioxide (SOx) compounds. Meaning, it helps to regulate exhaust emissions, which is important in countries where strict regulations are in place.
The EGR valve reduces the production of these gases by recirculating a regulated amount of exhaust back into the intake manifold.
By mixing the inert gas into the air fuel charge, the result is lower temperatures in the combustion chambers. Since combustion temperatures are lowered, the formation of these gases is dramatically reduced.
This is the role of the EGR irrespective of the engine configuration being discussed.
The system works by opening and closing solenoid valves that are regulated by a diaphragm. The solenoid valves will open and close based on the amount of manifold pressure that they receive.
Types of EGR Valves
There are different types of EGR systems used for different engines. However there are two types of EGR Valves:
- Vacuum-operated EGR Valve
- Electronically Controlled EGR Valve
Signs of a Bad EGR Valve
As you might expect, having a bad EGR valve can be problematic.
Not to mention components like the catalytic converter will have to work harder due to higher exhaust gas temperatures and you run the risk of burnt exhaust valves.
The EGR valve can cause problems both in its open and its closed state.
1. Engine Performance
The first thing you'll notice are engine performance issues. A stuck 'open' or 'closed' EGR valve causes the air-to-fuel ratio to be negatively affected. Consequently, this decreases the engine’s power, lowers the acceleration rate, and reduces fuel economy.
A closed or restricted EGR valve results in an increased amount of NOx gas emissions. This results in engine knocks or pings and excess pollution and smog.
2. Rough Idling
An open EGR valve can create a vacuum leak. As a result, the combustion becomes incomplete, causing further rough idling and hesitation when accelerating. This stumble is quite noticeable. The vehicle could even stall.
When an EGR valve is stuck open it means that ALL exhaust gases are rerouted to the combustion chamber resulting in less oxygen that's needed for the correct air/fuel ratio. You may even smell fuel because at low revs not all fuel will burn.
3. Check Engine Light (CEL) is ON
Chances are that the onboard computer will pick up the EGR problem by turning your check engine light on.
It could turn on when the EGR is either open or closed. It's important to note that an EGR valve will usually degrade before it fails and the CEL may not turn on until it fails.
A CEL that's on could mean a number of things. If you own an OBD-II scanner, consider using it to check for error codes. For instance, OBD-II fault code P0401 indicates that the exhaust EGR flow is insufficient.
EGR Replacement Cost
The replacement cost of an EGR can vary based on the make and model of your vehicle and its engine type. You also need to factor in the cost of parts and labor. There may also be added taxes and fees based on where you live.
The replacement cost of an EGR valve is $300-$500. Labor costs are estimated at $80-$110. The parts are $250-$350.
An EGR valve should be cleaned every 50,000 miles.
An EGR valve replacement is one of the less common repairs you should expect.
However, vehicles that only drive in residential areas or for quick-trips are prone to carbon build-up. EGR is typically the most active when an engine idles or makes short trips.
Driving on the highway and getting the engine to higher RPM ranges with a load can cause the deposits to get hot, break-up, and run through the engine.