What should a pilot do if the engine begins to run roughly due to vaporization of fuel during flight?

When an engine runs roughly due to fuel vaporization, it indicates that the fuel may not be reaching the engine in a proper, consistent manner. This can happen at higher altitudes where the temperature and pressure conditions can contribute to fuel losing its liquid state and turning into vapor.

Operating the boost pump serves to increase the fuel pressure and help prevent vapor lock by ensuring that enough fuel gets to the engine. The boost pump draws fuel from the tanks and pressurizes it, which can help overcome the issue that is causing the fuel to vaporize. This action can stabilize the fuel flow and improve engine performance, allowing the pilot to restore normal engine operation.

Reducing throttle could potentially worsen the condition by causing more vaporization if the engine is not receiving adequate fuel. Switching off electronic systems is generally unnecessary in this scenario, as electronic systems are not directly related to fuel delivery or the vaporization issue. Descending to a lower altitude could help alleviate the problem, but operating the boost pump provides a more immediate and effective remedy to stabilize the engine's performance and is typically considered the best initial action to take when facing fuel vaporization issues.