The EGR valve is a notorious problem area on old cars. This pollution-control device is designed to redirect controlled amounts of exhaust gas back into the intake manifold so they can be burnt off and reduce NOx emissions.
While the principle is simple, the high temperatures and soot can cause the valves to stick in either the open or closed positions. As a result, your engine can present starting, idling or drivability issues and create tailpipe pollution that is beyond the allowable limits for an emissions test.
When Your EGR Valve Sticks Open
- Rough idle, especially when the car is cold — when your car feels like it is stumbling or about to stall
- The smell of fuel in the tailpipe exhaust — this is unburnt fuel passing through the exhaust
- A check engine light (CEL) or malfunction indicator light (MIL) on your dash
- An increase in fuel consumption compared to what you're used to seeing with your Mercedes
- A failed emissions test due to high level of hydrocarbons present in your tailpipe emissions
These are all possible symptoms that your Mercedes EGR valve is stuck open. Your EGR valve is no longer able to regulate the amount of exhaust gas entering your intake, throwing off the precise gas/air flow in your combustion chambers.
When Your EGR Valve Sticks Closed
AN EGR valve can also get stuck in the closed position. While this can present some different symptoms than with your valve stuck open, in both cases, your engine will not run properly. You can also do serious long-term damage to your engine and pollution control system if you don't have your Mercedes' EGR valve repaired or replaced. Watch for symptoms such as:
- Uncharacteristic tapping or pinging noises from your engine at low speeds — early fuel detonation
- A check engine light (CEL) or malfunction indicator light (MIL) on your dash
- A failed emissions test due to high level of hydrocarbons present in your tailpipe emissions
- Secondary ignition of fuel after the primary ignition due to excess fuel in the exhaust vapors
An EGR valve that is stuck closed not only makes your car difficult to drive and causes more pollution, but the secondary detonations can cause serious damage to your engine if left unchecked.
Have Your Mercedes Inspected
If you experience any of these problems, it's important to contact a qualified Mercedes shop and have your EGR valve inspected. While these issues can often have different causes, they could indicate that your Mercedes EGR valve is faulty and that you have other serious problems with your engine control system, fuel delivery system, exhaust control system or other aspects of your engine.
Mercedes owners in the Chicago area are invited to contact our experienced team here at Burdi Motorworks, so we can diagnose your problems and fix or replace your EGR valve and get your Mercedes running perfectly again.