What is the reason for the dull engine sound?

The muffled sound of the engine may be caused by the abnormal operation of the cylinder. Check the throttle opening for serious carbon deposition. When the engine sounds dull, you can check the following components: 1. Checking the fuel supply system, replacing the gasoline filter and cleaning the injector will all affect the standard of engine fuel supply demand. 2. Check whether the power supply system and the ignition head of the spark plug are too large, which will slow down the frequency hopping and affect the combustion quality of the engine. It is recommended to replace. 3. Check whether the air filter of the air intake system is dirty or whether the air pipeline is aging or leaking. Cleaning the throttle will affect the air intake. 4. Check whether the exhaust system and three-way catalyst are blocked, which affects the smooth exhaust. Cleaning or replacement is recommended. 5. Check whether the engine cylinder pressure is up to standard and whether the standard cylinder pressure is greater than 8 kg. 6. Check whether the changed oil has the corresponding label. If the fuel level is too high or too much fuel is added, the engine sound will become dull.