When troubleshooting a rough running engine, which two other systems should be considered alongside the fuel delivery and metering system?

When diagnosing issues related to a rough running engine, it is crucial to consider the intake and ignition systems alongside the fuel delivery and metering systems. The fuel delivery system is responsible for providing the necessary fuel to the engine, while the metering system ensures the correct amount of fuel is delivered based on the engine's operating conditions.

However, the engine also requires the right mixture of air and fuel for optimal combustion, and this is where the intake system plays a vital role. It regulates the air entering the engine, which combines with the injected fuel for combustion. If there is a problem with the air intake, such as a clogged filter or a malfunctioning airflow sensor, it can lead to an incorrect air-fuel mixture, contributing to rough engine performance.

Ignition is equally important because it determines whether the fuel-air mixture will ignite at the right time. Issues in the ignition system, such as faulty spark plugs, ignition coils, or timing problems, can cause misfires, which would result in a rough running condition. Therefore, these two systems—intake and ignition—are directly related to the combustion process and must be evaluated when addressing engine performance issues, especially when they manifest as rough running.