Why did the tachometer first drop from the instantaneous position 1500 to 200 rpm and then back to 800 rpm after the throttle was cleaned?

You too! This phenomenon will occur after the general vehicle cleans the throttle, which is the throttle adaptive function. Some vehicles need a special decoder to match the throttle to enter the normal state, otherwise the engine will not accelerate and the power will drop. If my answer is helpful to you, please adopt it! thank you