How to reduce the belt speed of Dongfeng Civic accelerator after cleaning to 1200 rpm?

Do you live in the north? If it is in the north, in winter, the idle speed of Civic cold car is about 1500 rpm, and the hot car will be fine. Last winter in the northeast, it was frozen all night, and the next day the idle speed of driving could reach 1600 rpm. Please see if the idle speed returns to normal when the car is driving. It will be normal if we can return to 1000 rpm. If not, it may be that the idle speed has been raised during cleaning.