"Sparkling in the sunlight, Marcus looked at his new car". This is wrong. The correct version is: "The car's sparkling in the sunlight, Marcus looked at his new car".What has been bold typed stands for the subject of the present participle, sparkling. This subject is realised by the genitive case and it is a different subject from the main sentence / clause. What sparks is the car not Marcus. " With a grin of appreciation, the car looked almost brand new." wrong. The correct version is: " Marcus , with a grin of appreciation on his face, noticed the car ; the car looked almost brand new." The new version- elements in bold type - has turned into an idependent sentence / clause. Marcus is the one that wears a smile at noticing his brand new car. The semi colon stands for "since". "Grabbing the keys, the car was ready for a road trip." This is wrong. The right version is " Marcus' grabbing the keys ; the car was ready for a road trip". The subject of the present participle , grabbing , has to be provided since it is Marcus that grabs the key ,not the car. The semi-colon claims importance for it stands for because.