If a vehicle's STFT is stable at -10% and LTFT is at -22%, what might be responsible for excessive fuel consumption?

When assessing fuel trims, a stable short-term fuel trim (STFT) at -10% indicates that the engine control module (ECM) is adjusting the fuel mixture slightly richer by reducing fuel injector pulse width. Meanwhile, a long-term fuel trim (LTFT) at -22% means that the ECM has been compensating for a consistent lean condition over time by reducing fuel delivery by a larger amount.

The significant difference between the STFT and LTFT suggests that the vehicle has been experiencing a persistent fuel delivery issue, likely due to incorrect fuel pressure. A faulty fuel pressure regulator can lead to low fuel pressure, causing the engine to be starved for fuel, which would result in the need for the ECM to adjust fuel trims negatively to compensate for this lean condition. Therefore, the combination of a stable STFT and a significantly negative LTFT points towards a problem related to fuel delivery, solidifying that the fuel pressure regulator is likely responsible for the excessive fuel consumption observed.

While other options like a faulty throttle position sensor, leaking fuel injector, or clogged catalytic converter could impact fuel consumption, they would typically present with different fuel trim readings or symptoms. A leaking fuel injector, for instance, would likely cause a rich condition and have a