Why is my check engine light flashing and my car shaking?

A flashing check engine light is not the same as a steady one — it means an active misfire is dumping raw fuel into the exhaust, and that can destroy a catalytic converter in minutes. Combined with shaking, you're looking at one or more cylinders not firing: a failed ignition coil, a worn spark plug, a bad injector, or a vacuum leak. Pull over when it's safe, avoid heavy throttle, and get the codes read before driving further — a $60 coil now versus a $1,200 catalytic converter later is the whole decision.

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