There is a smell of gasoline behind the new Jetta, and there is an abnormal sound like a water pipe leaking. What happened?

Hello, it may be that there is too much carbon deposit in the engine, and the gasoline sprayed by the fuel injection head will be absorbed by a large amount of carbon deposit during cold start, which leads to too thin mixture during cold start and difficult start. Gasoline absorbed by carbon deposits is easy to enter the car after it is saturated. After entering the car, the gasoline adsorbed on the carbon deposit will be sucked into the cylinder by the vacuum suction of the engine for combustion, which will make the mixture rich, and the combustible mixture of the engine will be diluted and concentrated at other times, resulting in abnormal idle speed after cold start. I suggest you check it according to the situation.