The exhaust gas recirculation (EGR) valve does exactly what the name implies. It circulates exhaust gas for a second time.
Exhaust gas recirculation (EGR) valves do not normally require maintenance; but can become clogged with carbon deposits.
Carbon deposits can cause the exhaust gas recirculation (EGR) valve to stick, or prevent it from opening or closing properly.
An exhaust gas recirculation (EGR) valve that’s stuck open; will act like a vacuum leak and cause a rough idle and stalling.
An exhaust gas recirculation (EGR) valve that has failed; refuses to open will allow elevated emissions and may also cause detonation (spark knock).
Different Valve Types That Do The Same Job:
- Ported (EGR) valves (1973 to 1980s).
- Positive backpressure (EGR) valves (1973 & up).
- Negative backpressure (EGR) valves (1973 & up).
- Pulse-width modulated electronic (EGR) valves (early 1980s & up).
- Digital electronic (EGR) valves (late 1980s to 1990s).
- Linear electronic (EGR) valves (early 1990s & up).
Exhaust Gas Recirculation (EGR) Valve Failure Symptoms
Most (EGR) valve failures happen because the valve itself gets stuck open or closed. This is due to build up of soot particulates; carbon deposits and a sticky tar like substance. So, a faulty (EGR) valve should cause an ‘engine check’ light to turn on. This is to inform the driver that something that affects the engine’s emissions is not working correctly. However, before getting to total failure; the (EGR) valve will slowly degrade in operation.
As a result, causing it to react slower to input and partially stick. If the valve is stuck fully closed; it would cause higher temperatures within the cylinder; theoretically leading to knocking.
However, as most modern engines have knock sensors; they’ll most likely adapt and it probably won’t feel all that different. Most likely it will stick open when it should not. Causing a rough idle leading to a reduction in performance.
This degradation over time will be slow but should be noticeable. It will also mean worse fuel economy. Carbon deposits accumulate rapidly; especially if most of your driving happens within the city and short trips. This driving pattern doesn’t allow the engine to reach operating temperature; and run long enough to remove harmful carbon deposits.
Exhaust Gas Recirculation (EGR) Valve Cleaning
Depending on the (EGR) valve; it may be possible to extend its life by cleaning it rather than replacing it. However, to do the job thoroughly you’ll need to remove the valve to clean it. Consequently, this could end up taking more time than replacing it with a new valve. But, if successful will obviously be a cheaper fix.
Exhaust Gas Recirculation (EGR) Valve Replacement
Most DIY mechanics should be up to the task of replacing an (EGR) valve. We’d recommend taking pictures of the engine bay and connections to and from the (EGR) valve. Let the engine cool down; disconnect the battery and wait a few minutes for the electrical system to discharge completely. Isolate the battery terminals as well to prevent shorting. Finally, before removing anything; check that the replacement (EGR) valve you’ve bought looks identical to the old one.
If the (EGR) valve has vacuum pipes to it, label them before twisting and pulling the pipes off. Then carefully take off any electrical connections. This should be possible by hand, even if they are tight.
The valve itself may be mounted within a sturdy outer body; bolted to the cylinder head. Because, it has hot exhaust gases going through it; at times the bolts holding it on may be particularly tight.
So, it’s always a good idea to spray these bolts with a lubricant such as WD40. Consequently, this will help remove stuck bolts. Once the bolts are all off, take the valve and body out. Finally, remove any remnants of any old gaskets.
Simply reverse the process above with the new valve to fit it to the engine.
Find out what kind of (EGR) valve is on the vehicle so you can use the appropriate test procedure. Examine the valve or refer to a service manual. Also, on some vehicles, you may find this information on the underhood emissions decal. Also, find out what kind of vacuum controls are used in the vacuum plumbing.
Does it have a ported vacuum switch or a solenoid? Finally, follow the vacuum connections from the valve; refer to a service manual or the underhood emissions decal for vacuum hose routing information.
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