Symptoms of a Bad EGR
When combustion reactions reach high temperatures, nitrogen gas--which is otherwise inert--can react with oxygen to form nitrogen oxides like NO or NO2. The latter compound is especially infamous as a major contributor to air pollution. To reduce the amount of NO2 cars emit, most engines are equipped with an exhaust gas recirculation (EGR) system. Unfortunately, if the EGR system isn't functioning properly it can cause problems.
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What the Valve Does
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The EGR system is designed to return some of the exhaust into the air intake manifold, but only in a limited amount and under certain conditions. That's because recirculating exhaust gas into the combustion chamber reduces peak power and can cause unstable combustion at idle. The EGR is built with a valve to regulate the amount of exhaust gas returned to the intake manifold. If the EGR malfunctions or the valve is leaking, it can impair your engine's performance.
Symptoms
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A troublemaking EGR valve typically exhibits several symptoms: rough idle, reduced power, stalling and/or hesitation after you press on the gas pedal. These symptoms could also stem from other engine problems, however, so if you're experiencing these problems, test the EGR valve to make sure it's the culprit. The procedure you use to test the valve will vary between different engines, but there are some basic principles common to all of them.
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Plunger
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EGR valves have a plunger that opens and closes the valve with a slender steel shaft. Locate the EGR valve and the plunger; observe it while you rev the car in park. If the plunger is stuck open or closed, the EGR valve is probably faulty. EGR valves typically have a spring that returns the plunger to the closed position. You can test the spring tension by moving the plunger. If the spring is weak the EGR valve may be defective and need replacing.
Vacuum Lines
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The EGR system in most cars uses the vacuum in the intake manifold as an input that helps determine when the valve opens. Always check the vacuum lines leading to the EGR for leaks, cracks or breaks; these could cause EGR malfunction.
Valve Variation
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EGR valves in different makes and models are often designed differently; in many newer models, for example, the ECM (the electronic control module or "brain) may store a trouble code if it detects EGR malfunction. For more specific testing and diagnostic procedures, consult your car repair manual.
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References
- Photo Credit Motorcycle exhaust image by Crisps85 from Fotolia.com
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Comments
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oh yeh I forgot to say when it idels , and it idels rough it so rich my eyes tear.
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I have a 88 yj jeep with a carb , but this jeep runs great you can balance a nickel on the valve cover. I filled up at sunoco and three miles down the road it started missing / stalling just runing poor, now the last two weeks or so when I took off it kind of have a fast flat spot. it never had that so in my heart I new somthing was coming soon and here we are , I have been doing a lot of reading and I think the way its acting up it might be the egr valve.can I please have your input , thank you so much.
