What Causes the Idle Speed to Increase When Depressing the Clutch to Shift Gears?

[Roberto]

The reason for the idle speed increasing when depressing the clutch to shift gears is that the throttle is not fully released. When driving, the engine has rotational inertia (momentum) during operation. However, because there is a load (before the clutch is depressed), releasing the throttle will cause the speed to decrease. But during the process of speed reduction, suddenly depressing the clutch all the way results in significant rotational inertia, yet the load is suddenly removed, causing the speed to slightly increase instead. Solution: After fully releasing the throttle, wait a moment before depressing the clutch to shift gears. Essentially, it's a matter of coordinating the timing between the throttle and the clutch. Idle Speed Overview: Idle speed is an operational state of a car, referring to the engine running in neutral. The engine speed during idle is called the idle speed. The idle speed can be adjusted by modifying the throttle opening size, among other methods. Idle speed means the engine is "producing power without doing work."