P0304: Cylinder 4 Misfire Detected
What this check-engine code means in plain English, what usually causes it, and what a fix typically costs.
What P0304 means
The engine control module has detected that cylinder 4 is not firing properly or consistently. A misfire means the air-fuel mixture in that cylinder isn't igniting correctly, causing rough running, power loss, and potentially damaging the catalytic converter with unburned fuel.
What causes P0304?
Is P0304 safe to drive?
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 that can cause immediate damage.
P0304 repair cost
Industry-average estimates. Cost depends on the root cause: spark plugs are inexpensive, but compression issues or catalytic converter damage from delayed repair can be very costly.
Which one is it for your car?
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