Hello, have the problem with my S60 that oil coal has deposited at the throttle valve. The gap is reduced by the deposited oil coal and the engine can no longer regulate properly. This is expressed: when the engine is cold: the engine turns high to heat the cat faster after starting; the speed drops after a few seconds direction of stationary gas speed the engine starts to shake and goes out almost. As soon as you give gas it recovers. with warm engine: during the ride you press the clutch (e.g. when switching) the speed is below the current gas speed and you have the impression that the engine can not control the speed so quickly and almost wants to run out. The remedy is to clean the throttle flap. Has anyone ever done this and can give me tips? Can one reduce the oil carbon deposits by using fully synthetic engine oil (e.g. drive a half-synthetic HC 5W40 from Shell)? Can someone recommend a cleaner By the way, the problem can only occur until model year 2003, as Volvo has changed the throttle valve from 2004. Ciao, Eric, waiting for input THANK YOU in advance