What Causes Unstable Idle in the Encore?

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Unstable idle in the Encore may be due to a dirty throttle body, a faulty oxygen sensor, a malfunctioning coolant temperature sensor, or excessive carbon buildup on the spark plugs. Dirty Throttle Body: When hot oil vapor meets cold air or when the car is turned off, some oil vapor condenses on the back of the throttle body. Additionally, gasoline injected into the intake manifold may also condense on the throttle body when the engine is shut off. Over time, this leads to a dirty throttle body. Excessive Carbon Buildup on Spark Plugs: If the engine burns oil, the air-fuel mixture will not combust completely, leaving oil residue on the spark plugs, which accumulates over time. This can cause the spark plug gap to become too small, reducing ignition energy and slowing the combustion rate of the air-fuel mixture, resulting in decreased engine power. Solutions: Clean the throttle body; use a specialized automotive diagnostic tool to check for fault codes; replace the spark plugs.