Клапан холостого хода закоксован

On engines with a mechanical throttle, the valve that bypasses air around the closed plate to control idle, fouled with carbon so it can no longer meter accurately. It is the predecessor of electronic throttle control and appears on older vehicles, where idle is the one thing the module can still influence directly.

Fouling narrows the passage, so the valve runs further open to achieve the same airflow until it reaches the end of its range and the module reports that it is out of authority. The complaint is a hunting or stalling idle, worst when cold and when the air conditioning or another load is applied — precisely when the most bypass air is needed.

It is one of the few components where cleaning is a genuine repair. The passage and the pintle can be cleaned and the valve refitted, and it is worth doing before replacement. Check the throttle plate's own seating in the same pass — a plate that no longer closes fully feeds air past the valve's control entirely, which produces the identical symptom with a clean valve fitted.