一些比较菜的车系，一旦发动机亮黄灯，运转不平稳，obd code会直接了当告诉你几号coil ／火花塞bad了，换件即可

Google forum:

Engine overheating: When a faulty ignition coil is ignored for long enough, it may overheat, which can cause serious damage to the rest of the engine.

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Over longer miles, you do take a risk with unburned gas ending up in the catalytic converter and poisoning the catalyst, ultimately closing the pores in it. However, small miles driven may not matter.