P0314 – Single Cylinder Misfire Detected (Cylinder Not Specified) means the engine control unit has detected a misfire event, but the ECU cannot determine which specific cylinder is responsible. This usually happens when the misfire is too intermittent, too mild, or occurs under conditions where cylinder contribution data is unclear. Misfires can cause rough running, hesitation, poor fuel economy, and potential catalytic converter damage if ignored. This guide explains what P0314 means, its symptoms, causes, diagnosis steps, and the best repair solutions to restore proper engine performance.
What Does P0314 Mean?
P0314 is a generic OBD-II DTC that indicates the ECU detected a misfire but could not assign it to a specific cylinder, unlike codes such as P0301 or P0304. The ECU typically uses crankshaft speed fluctuations to identify which cylinder misfires, but when the signal is weak, noisy, or inconsistent, it logs P0314 instead.
This code often appears alongside other misfire or fuel trim codes and can point to ignition problems, fuel starvation, or airflow issues affecting one cylinder more than others.
Quick Reference
- OBD-II Family: P-Code (Powertrain)
- Scope: Generic
- System: Ignition / Fuel / Air / Mechanical
- Difficulty Level: Moderate
- Estimated Repair Cost: €70–€450+
- Last Updated: 7 December 2025
Real-World Example / Field Notes
A sedan arrived with intermittent vibration at idle and P0314 stored. Freeze-frame data showed the misfire happening only when the engine was cold. The spark plugs were severely worn, and one plug had a cracked insulator. Replacing all plugs eliminated the misfire and prevented further damage.
Another case involved a vehicle that set P0314 at high speeds. The fuel pump could not maintain pressure under load, causing occasional lean misfires that the ECU could not pinpoint. After installing a new pump, the engine ran smoothly and the code did not return.
Symptoms of P0314 – Single Cylinder Misfire Detected
- Rough idle: Engine may shake at low RPM.
- Hesitation: Brief stumbles during acceleration.
- Loss of power: Reduced performance under load.
- Poor fuel economy: Wasted fuel due to incomplete combustion.
- Check engine light: May flash during severe misfires.
- Fuel smell: Unburned fuel reaching the exhaust.
Common Causes of P0314
Most Common Causes
- Worn or fouled spark plugs
- Failing ignition coil (intermittent)
- Restricted or leaking fuel injector
- Low fuel pressure or weak fuel pump
- Vacuum leaks causing lean misfires
Less Common Causes
- Dirty or failing mass airflow (MAF) sensor
- Contaminated fuel or water in tank
- Camshaft or crankshaft sensor signal noise
- Mechanical problems such as low compression
- ECU software or internal driver fault (rare)
Diagnosis: Step-By-Step Guide
Because the offending cylinder is not specified, diagnosing P0314 requires checking ignition, fuel, air, and mechanical components across all cylinders.
Tools You’ll Need
OBD-II scanner with Mode $06 misfire counters, spark tester, multimeter, fuel pressure gauge, smoke machine, compression tester, and basic tools.
- Review freeze-frame data: Note RPM, load, temperature, and trims during the misfire.
- Check Mode $06 data: Some ECUs still show cylinder misfire counts even when P0314 is logged.
- Inspect spark plugs: Check all plugs for cracks, carbon buildup, or oil fouling.
- Test ignition coils: Swap suspect coils between cylinders to identify intermittent faults.
- Perform injector balance test: Check for restricted or leaking injectors.
- Check for vacuum leaks: Smoke-test intake system and PCV lines.
- Clean and test MAF sensor: Incorrect airflow data can cause lean misfires.
- Measure fuel pressure: Confirm pump and regulator performance.
- Perform compression test: Identify mechanical issues such as worn rings or valves.
- Inspect crank and cam signals: Signal dropouts can confuse misfire detection.
Pro Tip: Use Mode $06 “misfire monitor” data even when the ECU cannot identify a specific cylinder. Many vehicles still store per-cylinder misfire counts there.
Possible Fixes & Repair Costs
- Replace spark plugs: €20–€80
- Replace ignition coil: €50–€120
- Clean or replace fuel injectors: €120–€280
- Repair vacuum leaks: €50–€150
- Clean or replace MAF sensor: €20–€150
- Replace fuel pump or filter: €80–€350+
Can I Still Drive With P0314?
Driving short distances may be possible, but it is not recommended. If misfires worsen, the engine can stall or damage the catalytic converter. A flashing check engine light means the misfire is severe—stop driving immediately to avoid costly repairs.
Related Codes
- P0399 – Ignition Coil “R” Primary/Secondary Circuit
- P0364 – Reserved
- P0363 – Misfire Detected Fueling Disabled
- P0362 – Ignition Coil “L” Primary/Secondary Circuit
- P0361 – Ignition Coil “K” Primary/Secondary Circuit
- P0360 – Ignition Coil “J” Primary/Secondary Circuit
- P0359 – Ignition Coil “I” Primary/Secondary Circuit
- P0358 – Ignition Coil “H” Primary/Secondary Circuit
- P0357 – Ignition Coil “G” Primary/Secondary Circuit
- P0356 – Ignition Coil “F” Primary/Secondary Circuit
Key Takeaways
- P0314 indicates a misfire but does not identify the cylinder.
- Ignition, fuel delivery, and airflow issues are the most common causes.
- Mode $06 data can help pinpoint the exact cylinder.
- Early diagnosis prevents catalytic converter damage.
FAQ
Why doesn’t P0314 specify a cylinder?
The ECU stores P0314 when misfire data is too weak, inconsistent, or noisy to identify which cylinder is misfiring.
Can bad fuel cause P0314?
Yes. Contaminated or low-quality fuel can cause intermittent misfires across multiple cylinders.
Will P0314 go away after refueling?
If the misfire was caused by low fuel or temporary fuel starvation, refueling may resolve the issue.
How do I find which cylinder is misfiring?
Check Mode $06 misfire counters or swap ignition components between cylinders to isolate the faulty one.
Is it safe to ignore P0314?
No. Misfires can cause catalytic converter damage and degrade engine performance if not repaired promptly.