P0304 What does it mean?
Can you drive, what causes it and how it shows.
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Common codes
P0304
Cylinder 4 Misfire Detected
Misfires concentrated on cylinder 4. A cylinder-specific code points away from shared causes (fuel pressure, MAF) toward components dedicated to that cylinder, coil, spark plug, injector, compression. Verify by swapping the suspected coil/plug to a different cylinder; if the code follows, the part is bad.
Can you drive?
“You can drive, but see a mechanic soon”. The engine is misfiring. If the check light is flashing, stop: the catalytic converter is burning.
9,533trouble codes explained in plain words, free.
What causes it
The most likely cause comes first. Some you can fix yourself.
- 1Ignition coil for cylinder 4 failed
- 2Spark plug for cylinder 4 worn or fouled
- 3Cylinder 4 injector clogged
How it shows
Usually it shows like this.
- Check engine light on or flashing
- Rough idle and uneven running
- Power loss, hesitation under acceleration
- Increased fuel consumption
- Possible smell of unburned fuel from exhaust
In the app
Partly freeExplaining a trouble code is free: 9,533 codes, offline. With an adapter the app reads the code itself and tells you whether you can drive. A sample scan is free; unlimited scans come with VINARI+.
Common questions
What does P0304 mean?
P0304: Cylinder 4 Misfire Detected. Misfires concentrated on cylinder 4. A cylinder-specific code points away from shared causes (fuel pressure, MAF) toward components dedicated to that cylinder, coil, spark plug, injector, compression. Verify by swapping the suspected coil/plug to a different cylinder; if the code follows, the part is bad.
Can I drive with P0304?
“You can drive, but see a mechanic soon”. The engine is misfiring. If the check light is flashing, stop: the catalytic converter is burning.
What causes P0304?
Most often: Ignition coil for cylinder 4 failed, Spark plug for cylinder 4 worn or fouled, Cylinder 4 injector clogged.
How do I find out which code my car has?
Plug an ELM327 OBD adapter into the OBD-II port under the steering wheel and tap “Scan” in VINARI. The app reads the code, explains it and tells you whether you can drive.
Do I still need a mechanic?
Yes. The app tells you what is going on and how urgent it is; the final word belongs to the mechanic.
Other topics
Source: OBDex (CC0), VINARIUpdated 2 November 2026
