What Causes High Idle Speed in Nissan Bluebird?

1 Answers
DelAdaline
07/30/25 1:25am
There are three main reasons for high idle speed in Nissan Bluebird. Idle switch not closing: The rotation speed signal determines the fuel injection volume and injection timing. When the engine is operating under idle conditions with reduced air intake, this leads to an over-rich air-fuel mixture and consequently increased engine speed. Malfunctioning idle control valve: When the idle speed exceeds the preset value, the ECU commands the idle control valve to reduce the bypass air intake, thereby decreasing engine speed. Issues like sticking due to oil contamination/carbon buildup or incomplete throttle valve closure can prevent the ECU from properly regulating idle speed, resulting in unstable idling. Intake manifold air leakage: The opening degree of the idle control valve and air intake strictly follow a specific functional relationship - increased valve opening corresponds to greater air intake. Air leakage disrupts this relationship, making the air flow sensor unable to measure actual intake volume accurately. This causes imprecise ECU air intake control and unstable engine idle.
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