What adverse effect can occur if a diesel injector becomes clogged?

When a diesel injector becomes clogged, it can lead to uneven distribution of fuel into the combustion chamber, which directly impacts the engine's performance. The injector’s primary function is to atomize the fuel and ensure a steady supply for efficient combustion. If it is clogged, fuel may not be delivered properly, resulting in incomplete combustion. This can cause rough engine performance characterized by symptoms such as misfiring, stumbling, or a noticeable drop in power during operation.

Rough performance can be due to an imbalance in the air-fuel mixture, leading to fluctuations in engine speed and acceleration. This not only affects the immediate operation of the engine but can also cause undue stress on engine components over time, potentially leading to further mechanical issues.

In contrast, the other outcomes listed, such as increased fuel efficiency, engine overheating, and lower emissions, would typically not be associated with a clogged injector. Instead, a clogged injector is more likely to reduce fuel efficiency and increase emissions due to the improper combustion process. Thus, rough engine performance emerges as the most relevant and critical consequence of a clogged diesel injector.