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P0301: Cylinder 1 Misfire Detected

What this check-engine code means in plain English, what usually causes it, and what a fix typically costs.

Severity: Urgent — can cause catalytic converter damage if driven extensively

What P0301 means

The engine control module has detected that cylinder 1 is not firing properly or consistently. This means the air-fuel mixture in that cylinder is not combusting correctly, causing rough running and potential damage to emissions components.

What causes P0301?

Likely
Faulty spark plug or ignition coilWorn spark plugs or a failing ignition coil on cylinder 1 are the most common causes of single-cylinder misfires.
Likely
Fuel injector problemA clogged or malfunctioning fuel injector for cylinder 1 can prevent proper fuel delivery and cause misfires.
Possible
Low compression or valve issuesWorn piston rings, damaged valves, or head gasket leaks can reduce compression in cylinder 1 and prevent proper combustion.
Less common
Vacuum leak or intake manifold gasketA vacuum leak affecting cylinder 1 can create a lean condition that causes misfires under certain conditions.

Is P0301 safe to drive?

Drive it?
Short distances only, avoid highway speeds
Watch for
Rough idle, loss of power, strong fuel smell, or flashing check engine light
DIY-friendly?
Swapping spark plugs and coils is beginner-friendly; other causes require more expertise

You can drive short distances carefully, but continued driving with a misfire sends unburned fuel into the catalytic converter, which can overheat and destroy it—a very expensive repair. If the check engine light is flashing, stop driving immediately as this indicates severe misfiring.

P0301 repair cost

~$100 – $1200+

Industry-average estimates. Cost depends on the root cause: spark plugs are inexpensive, but compression issues or catalytic converter damage from prolonged misfiring can be costly.

Which one is it for your car?

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