The engine noise on my '84 300d is louder on cold mornings. Last time I ended up getting the charger out to get it going. When I unplugged the charger I really noticed the noise, sounded like it was louder than usual combustion, this might also be called injector "nailing".(?) Hopefully it will do better with a valve adj., in the cold (20f) with no block heater it takes a minute of engine shaking and smoking along with a louder engine before it smooths&quiets out.