When you start a car and put it in drive is there supposed to be a slight shake in the engine or should it be just as smooth as when in park?

When you are sitting with your foot on the brake and the engine running and you select drive, depending on the quality of your vehicle, there might be a slight jolt or thump as the engine is then suddenly trying to move the car along the ground. So if the tick-over

speed is too low the sudden extra effort could slow it down further and make it run less smoothly. When the selector is moved from park to drive, there are no gears engaging, only a clutch and or brake band to start engaging, this should happen fairly smoothly with no mechanical noise apart from that already mentioned.