What makes your car run? Well, it's hard to explain. Your car engine is a big ball of wibbly wobbly timey wimey stuff. If it breaks, take the car to your neighborhood auto mechanic and TARDIS technician. Tumblr blogger Traci took her car to one, who, after seeing all of the Doctor Who-themed paraphernalia inside, left an appropriate note.
The reference to the "thingy that goes ding" is from this scene in "The Day of the Doctor."
"Round things" is a reference to another scene in that same episode.