Good evening dear Volvo municipality , After many good years my Volvo has the following problem when the engine is warm and I am standing at the traffic light, the engine jerks , while the speed varies between 500 and 700 revolutions . It lasts a few seconds then again well . When accelerating after the amp stop ruckeln at the first 20 meters , then everything ok . When driving on the expressway , this happens occasionally ruckeln . Was in the workshop , diagnostic device – no errors . Workshop has identified the Kat as an evildoer . This is too – thus exhaust jam and jerk . My question : can this be ? Does anyone have experience with this problem ? Would not like to install new Kat and keep the problem ? ? Best regards Miki 13