Why does a small car's engine shake when running at high speed?

[McIsaac]

Small car engine shaking at high speed may be caused by severe engine carbon deposits, engine misfire, or inconsistent air-fuel mixture. Severe engine carbon deposits: A very common cause of car shaking is excessively dirty throttle body or excessive carbon buildup in fuel injectors. When there's too much carbon deposit inside the engine, the gasoline sprayed by cold start injectors will be largely absorbed by carbon deposits; immediate carbon cleaning is required. Engine misfire: Engine misfire mainly refers to one or more cylinders not working properly, manifested as intermittent exhaust gas flow with noticeable pauses, severe exhaust pipe vibration, obvious engine shaking sensation, and sometimes accompanied by sputtering sounds. This is related to ignition coil failure; replacement of relevant ignition system components is needed. Inconsistent air-fuel mixture: Causes idle shaking after cold start. The lower the temperature, the more fuel required for cold start, and carbon deposits will affect whether cold start proceeds smoothly; replacement of front oxygen sensor is required. Engine shaking requires immediate vehicle inspection and maintenance, checking whether the ignition system, intake system, and fuel system have malfunctions. If malfunctions are found, immediate troubleshooting is necessary.