What's the reason for the sound of metal friction when stepping on the accelerator?

[SanMaria]

If this situation occurs, it should be due to carbon deposits in the intake system. Below is extended information about carbon deposits: 1. Introduction: Carbon deposits include two concepts: One concept refers to engine carbon deposits, which are a kind of coking substance produced by unsaturated olefins and gums in fuel under high temperatures during the engine's operation. The second concept refers to carbon deposits in electrical discharge machining, where carbon deposits should be avoided as much as possible, especially in precision mold processing, as they can have fatal effects. 2. Causes of formation: Carbon deposits in the combustion chamber are caused by tiny carbon particles produced after the explosion of gums in gasoline components and hydrocarbons that cannot be completely ignited. These black particles should be discharged into the atmosphere with the exhaust gas or accumulate on the muffler pipe.