Verona L6-2.5L (2005)
EGR Valve: Description and Operation
Exhaust Gas Recirculation Valve
The exhaust gas recirculation (EGR) system is used to lower oxides of nitrogen (NOX) emission levels caused by high combustion temperatures. The
main element of the system is the EGR valve which is operated electronically.
The EGR valve feeds small amounts of exhaust gas into the intake manifold to decrease the combustion temperature. The amount of exhaust gas
recirculated is controlled by the engine control module (ECM) in response to variations in engine load. If too much exhaust gas enters, combustion will
not take place. For this reason, very little exhaust gas is allowed to pass through the valve, especially at idle.
The EGR valve is usually open under the following conditions:
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Warm engine operation.
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Above idle speed.
Results of Incorrect Operation
Too much EGR flow tends to weaken combustion, causing the engine to run roughly or to stop. With too much EGR flow at idle, cruise, or cold
operation, any of the following conditions may occur:
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The engine stops after a cold start.
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The engine stops at idle after deceleration.
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The vehicle surges during cruise.
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Rough idle.
If the EGR valve stays open all the time, the engine may not idle. Too little or no EGR flow allows combustion temperatures to get too high during
acceleration and load conditions. This could cause the following conditions:
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Spark knock (detonation)
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Engine overheating
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Emission test failure
