That's likely normal. The Eco Throttle system reduces engine speed when electrical load is low, which makes the engine sound different.
Diagnosis: With Eco Throttle ON and minimal load connected, the engine runs slower and quieter. When you plug in a high-wattage appliance, the engine should speed up to meet the demand, and the noise will change.
When to turn Eco Throttle OFF:
- When connecting high electrical loads simultaneously (to reduce voltage changes).
- When using the DC receptacle for battery charging.
- If you prefer a constant engine speed regardless of load.
If the noise is a metallic rattle or knock: Stop the engine. Check that all cooling holes on the side panel, control panel, and bottom are clear of debris, mud, or water. Blocked cooling holes cause overheating and damage.
Heads up: For proper cooling, always operate the generator on a level surface with at least 3 feet of empty space above and around it.