The Idle Compensator is generally used on vehicles with air conditioning. When a vehicle comes to a stop and the engine is hot, the carburetor tends to richen up and even percolate (boil).
During these situations, the fuel may evaporate more than usual, causing a rich mixture, which can lead to poor idling or stalling. The hot idle compensator counteracts this by allowing more air into the mixture, making it leaner and helping the engine run more smoothly.
To do this, it typically contains a bimetallic spring. When the engine temperature increases, the heat causes the spring to contract, which opens a valve and allows more air to be drawn into the intake manifold, thus adjusting the air-fuel mixture.
Remember, the hot idle compensator is not common in modern vehicles which predominantly use fuel injection systems and have a multitude of sensors and a computer-controlled mechanism to ensure the optimal air-fuel mixture regardless of engine temperature or operating conditions.
