Q: Engine idle fluctuates

You may have a dirty or failing idle air control valve. The idle air control valve reads the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. Since this valve is controlled by the vehicle’s computer, it will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve. When the engine RPM drops below the normal range of about ~800 RPM, this often times will cause the engine to stall indicating a dirty or faulty idle air control valve. When you have the clutch depressed half way, the reason this may smooth out the idle is that this places the engine under a load that it may not otherwise be subjected to when the clutch is pressed all the way in. I would recommend having an expert from YourMechanic come to your location to diagnose and repair your idle air control valve.