What symptom may indicate a failing fuel injector?

Fluctuating RPMs can be a significant symptom of a failing fuel injector. When fuel injectors malfunction, they may not deliver the correct amount of fuel into the combustion chamber, leading to inconsistent engine performance. This inconsistency can manifest as erratic RPMs, where the engine speed fluctuates unexpectedly, causing a rough running condition.

In healthy fuel injector operation, the injectors must atomize fuel evenly to maintain consistent engine speed and performance. If one or more injectors are clogged, leaking, or damaged, it will result in uneven fuel distribution. This can cause the engine to hesitate, misfire, or not accelerate smoothly, all contributing to the observed fluctuation in RPMs.

Other symptoms like smooth engine operation or constant fuel odor, while they may suggest different issues, don't directly indicate failing injectors. An increased oil pressure could also arise from separate mechanical issues unrelated to fuel injector performance. Thus, fluctuating RPMs serve as a clear indicator of potential problems with fuel injectors.