When do you replace a variable valve timing solenoid?

A variable valve timing (VVT) solenoid should be replaced when you experience symptoms such as rough idling, poor acceleration, or a check engine light indicating a VVT-related trouble code. Additionally, if there's an oil leak around the solenoid or if the engine exhibits a lack of power or unusual noises, it's a sign that the solenoid may be failing. Regular maintenance and inspection can also help determine when replacement is necessary.