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Code

P0304

Ignition / Engine

Cylinder 4 misfire detected

Cylinder 4 is misfiring. Isolate by swapping parts.

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Most likely causes

Faulty spark plug or coil on cyl 4
Injector fault
Vacuum leak
Low compression

Symptoms you may notice

Rough idle
Shaking
Check engine light
Loss of power

Checks to run

Swap coil/plug to another cylinder
Test injector and compression on cyl 4

Tools you may need

OBD-II scanner Multimeter Compression tester

Always diagnose before replacing. Codes share symptoms; confirm the cause with measurements before buying parts.

Related codes in Ignition / Engine

Random / multiple cylinder misfire detected

Cylinder 1 misfire detected

Cylinder 2 misfire detected

Cylinder 3 misfire detected

Cylinder 5 misfire detected

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