P0304 meaning: Cylinder 4 Misfire Detected Explained
Understand P0304 meaning, common causes, and how to fix it. Learn DIY checks and when to consult a specialist for cylinder 4 misfire detection.
P0304 meaning is a diagnostic trouble code indicating a misfire detected in cylinder 4. This code appears when the engine control module (ECM) identifies inconsistent combustion in the fourth cylinder, disrupting engine balance and performance.
What P0304 Means
The P0304 code specifically signals a misfire in cylinder 4. It is part of the P0300 series, which covers random or multiple cylinder misfires. Unlike P0300 (which indicates random misfires), P0304 pinpoints cylinder 4 as the source. This code triggers the check-engine light and may affect engine smoothness, fuel efficiency, and emissions.
Most Common Causes of P0304
Cylinder 4 misfires typically stem from issues in ignition, fuel delivery, or mechanical components. The most frequent causes, ranked by occurrence:
- Faulty spark plug or ignition coil for cylinder 4
- Clogged or leaking fuel injector affecting cylinder 4
- Low compression due to valve or piston ring issues
- Vacuum leak near cylinder 4 intake manifold
- Damaged cylinder 4 wiring or sensor malfunction
What Shows on a Live Scan
During a live OBD2 scan, the P0304 code appears alongside specific PIDs. These include:
- Short Term Fuel Trim (STFT) for Bank 1
- Long Term Fuel Trim (LTFT) for Bank 1
- Misfire Count for Cylinder 4
- Throttle Position Sensor (TPS) voltage
Values vary by vehicle make, model, and engine type. For example, STFT might fluctuate between -10% and +15% during idle, while misfire counts rise during acceleration. Always verify live data against manufacturer specifications.
DIY-Safe Checks
Before seeking professional help, verify these simple fixes:
- Inspect the spark plug in cylinder 4 for fouling, wear, or incorrect gap. Replace if damaged.
- Swap the ignition coil from cylinder 4 with another cylinder’s coil. If the misfire code moves to a new cylinder, the coil is faulty.
- Check for vacuum leaks using a smoke test or carb cleaner spray around the intake manifold.
- Ensure the fuel injector connector for cylinder 4 is secure and free of corrosion.
Note: Never replace parts without confirming the issue. Misdiagnosis can waste time and money.
When to Consult a Specialist
Some P0304 cases require expert diagnosis. Seek help if:
- The code persists after replacing spark plugs, coils, and injectors
- Compression tests reveal low pressure in cylinder 4
- Multiple codes appear, suggesting interconnected system failures
- You lack tools to test fuel pressure, compression, or sensor signals
Cylinder 4 misfires can indicate serious internal engine issues. Running the vehicle with this code active may damage the catalytic converter or cause poor drivability. Always consult a specialist if symptoms include rough idling, loss of power, or fuel odor.
P0303 meaning: Cylinder 3 Misfire Detected Explained
P0300 meaning: Random/Multiple Cylinder Misfire Detected Explained
P0175 Meaning: System Too Rich (Bank 2) Explained
Talk to a specialist to diagnose your P0304 code accurately and avoid further engine damage. Find a verified electrician through our platform for reliable, expert support.
P0304 meaning requires careful attention. While some fixes are DIY-friendly, complex issues demand professional expertise to ensure safety and longevity of your vehicle.
P0304 meaning is best addressed with expert guidance. Don’t ignore persistent misfire codes — schedule a diagnostic session with a trusted specialist today.
P0303 meaning: Cylinder 3 Misfire Detected Explained
P0300 meaning: Random/Multiple Cylinder Misfire Detected Explained
P0175 Meaning: System Too Rich (Bank 2) Explained
Talk to a specialist to resolve your P0304 issue. Our platform connects you with certified auto electricians for fast, accurate diagnostics.