A vehicle with electronic fuel injection shows poor gas mileage and a rich mixture. Who of the following technicians is correct regarding the potential causes?

When diagnosing poor gas mileage paired with a rich fuel mixture in a vehicle equipped with electronic fuel injection, it’s important to understand what factors may contribute to this issue. A rich mixture indicates that there is too much fuel in relation to the air entering the combustion chamber.

Both technicians may suggest different causes or contributing factors that could lead to this condition. One technician may point towards issues such as a malfunctioning oxygen sensor, which can lead the engine control unit (ECU) to deliver excess fuel in an attempt to maintain the proper air-fuel mixture. Another technician might identify a faulty fuel pressure regulator, which could allow too much fuel to reach the injectors, causing a rich condition.

By acknowledging the validity of both technicians' assessments, you can conclude that they each recognize different, but potentially coexisting, causes of the rich mixture and poor gas mileage. This comprehensive overview indicates that multiple issues can lead to the same symptom, hence both technicians are correct in their assessment of the underlying problems that could cause a rich fuel mixture in an electronic fuel injection system.