A high-pitched shrill whistling coming from under the motor hood
I got a Toyota Vitz 1999. I am in search for a solution to the problem commonly found in all Toyota Vitz cars. I permanently hear, first it was only in winter but now in summer too, a high-pitched (nearly ultrasonic) whistling under the hood, roughly somewhere near the alternator. The whistling always appears when I accelerate the speed or decelerate it while driving, whereas no whistling sound occurs while driving smoothly. Some say it might be due to either the loosen (poorly tightened) alternator belt or the loosen timing chain. But this is not the case because I have them both certainly tensioned well to rule out this kind of high-pitched shrill whistling.
Maybe the reason is, the throttle valve or idle valve has been clogged with dirt making it a whistler and I should demount both and clean them from carbon deposit and lubricate the bearings?
Any other ideas or anybody knows how to get rid of the whistle?
