What if Jetta's throttle doesn't turn off?

Regarding your question, there are many factors that lead to high fuel consumption, such as driving habits (sudden refueling, sudden braking, neutral taxiing, mismatch between speed and gear), low tire pressure, inferior fuel, ignition system failure, electronic control system failure, etc. These failures will increase the fuel consumption of the vehicle. Secondly, if the vehicle is not maintained on time, such as not replacing the air filter, gasoline filter, spark plug and clutch plate in time, it will also lead to an increase in fuel consumption. Then there are carbon deposits and faults in the electronic control system, such as carbon deposits in throttle body, idle valve and fuel injector, and inaccurate signals of oxygen sensor, air flowmeter and water temperature sensor. These will affect the fuel consumption of vehicles. If the fuel consumption is too high, a comprehensive inspection is needed. I suggest you focus on checking whether the signals of each sensor are normal, whether the carbon deposition of each component is serious, and whether there is any problem with the added engine oil. Besides, your car has been running for almost 10 years, and it's time for a comprehensive inspection.