How to judge a broken fuel injector?

Fuel injector ,is a simple solenoid valve.  When the solenoid is energized, suction is generated, the needle valve is sucked up, and the nozzle hole is opened. The fuel is sprayed out at high speed through the annular gap between the needle at the head of the needle valve and the nozzle hole, forming a mist, which is conducive to complete combustion.

A broken engine fuel injector will cause the following symptoms:
1, Engine shaking
2,Power decreases and fuel consumption.
3,Difficult starting, whether the car is cold or hot, it is difficult to start, and even stalls while driving.
4, Exhaust gas emissions increase and pollutants are emitted.
5,The exhaust may emit black smoke and increase the production of carbon.

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