The 2001 Volkswagen Jetta features a number of improvements to the body style and internal components of the line, from a better-built "tiptronic" transmission to more integrated electronics. These computer-related upgrades make the vehicle more sensitive to slight variances in engine performance, like faulty oxygen sensors which can adversely impact fuel economy and potentially lead to the damage of other integral engine components. If your vehicle begins to use more gas than usual, take it in for an inspection to avoid potentially expensive repairs later.
A failing or dead oxygen sensor will prevent the Jetta's on-board computer from entering closed-loop functioning. This open mode of performance will cause fluctuations in the vehicle's air-to-fuel mixture resulting in a rich running engine. The Jetta will have a decrease in fuel economy and an increase in emissions as the vehicle operates in this "open mode."
While the Jetta is running rich, additional stress is placed on the catalytic converter. Increased heat on the component due to increased fuel consumption will push the converter past its prime operating temperatures. The driver will notice decreased acceleration; and as the oxygen sensor places more heat on the converter, there may be a full engine shutdown as the converter literally melts around itself, creating a complete blockage.
A faulty oxygen sensor in a fuel-injected engine, such as the 2001 VW Jetta, wreaks havoc with its fuel mixture. This can cause the vehicle to idle rough as the on-board computer attempts to compensate for excess fuel in the engine and draws more air. Additionally, the engine will misfire, when at lower speeds, due to the timing of the fuel injectors being thrown off by the odd mixture of air and fuel.
