Interference between variable parts. After BMW 320li replaced the lower arm, the squeak was caused by the impact or installation of other equipment, which made the two parts interact. It is caused by interference between changed parts. Only through plastic repair or replacement of related parts can parts not interfere with each other. BMW, called Bavarian Engine Factory Co., Ltd. in Chinese, is a German automobile brand. BMW has four models, I, X, Z and pure digital, 1.