C4l 1.8 Abnormal idling sound of cold car

If the idle speed of the cold car is high, the sound of the engine will be louder, but the normal sound based on the hot car! In order to distinguish, the engine speed can be artificially added to the cold car speed when the car is hot (1000 rpm-1200 rpm). In contrast, the sound is similar, so I will not consider it! In addition, the abnormal noise of cold car generally includes: 1: the valve tappet sounds, but it becomes smaller or disappears after hot car due to the aging of the tappet. Voice characteristics: Da. Da. The sound is very regular! 2. The chain link of the variable timing adjustment mechanism is also aging, the oil is sticky when the car is cold, and the pressure is not good! Sound characteristics: very sharp chain sliding sound