P0311 – Cylinder 11 Misfire Detected means the engine control unit has identified incomplete or inconsistent combustion occurring in cylinder 11. A misfire in this cylinder can cause rough idle, hesitation, poor acceleration, increased fuel consumption, and potential catalytic converter damage if unburned fuel enters the exhaust. This guide explains what P0311 means, its symptoms, causes, diagnostic steps, and the best repair options to restore proper engine performance.
What Does P0311 Mean?
P0311 is a generic OBD-II trouble code indicating the ECU has detected repetitive or severe misfire events in cylinder 11. The ECU uses crankshaft acceleration data and cylinder contribution monitoring to identify cylinders producing weak combustion. When cylinder 11 consistently fails to burn the air-fuel mixture properly, P0311 is stored.
Rapid diagnosis is essential because prolonged misfires can overheat and damage the catalytic converter, resulting in costly repairs.
Quick Reference
- OBD-II Family: P-Code (Powertrain)
- Scope: Generic
- System: Ignition / Fuel / Air / Mechanical
- Difficulty Level: Moderate
- Estimated Repair Cost: €70–€400+
- Last Updated: 5 December 2025
Real-World Example / Field Notes
A commercial V12 engine came in with harsh vibration and reduced power output. Cylinder contribution testing revealed cylinder 11 firing weakly. The spark plug was oil-fouled due to worn valve stem seals. After replacing the seals, plug, and coil, engine smoothness returned and P0311 cleared.
Another example involved a performance V12 vehicle misfiring only at high RPM. The ignition coil for cylinder 11 showed insulation breakdown under load. Replacing the coil and plug restored clean combustion across the full RPM range.
Symptoms of P0311 – Cylinder 11 Misfire Detected
- Rough idle: Shaking or uneven running at low RPM.
- Loss of power: Hesitation or weak acceleration under load.
- Poor fuel economy: Wasted fuel due to incomplete combustion.
- Check engine light: Steady or flashing depending on severity.
- Fuel smell: Unburned fuel entering exhaust.
- Engine stalling: Severe misfires can cause the engine to stall.
Common Causes of P0311
Most Common Causes
- Worn or fouled spark plug in cylinder 11
- Faulty ignition coil or damaged coil boot
- Restricted or leaking fuel injector (cylinder 11)
- Vacuum leak near the cylinder 11 intake runner
- Failing or contaminated mass airflow (MAF) sensor
Less Common Causes
- Low compression caused by valve, piston, or ring wear
- Camshaft or crankshaft position sensor malfunction
- Weak fuel pump or failing pressure regulator
- Carbon buildup affecting cylinder 11 combustion
- Rare ECU driver failure affecting injector or coil control
Diagnosis: Step-By-Step Guide
Diagnosing P0311 requires thorough inspection of ignition components, fuel delivery, mechanical condition, and intake system integrity.
Tools You’ll Need
OBD-II scanner with misfire data, spark tester, multimeter, compression tester, fuel pressure gauge, smoke machine, and basic tools.
- Review freeze-frame data: Check RPM, load, temp, and fuel trims at the moment the misfire occurred.
- Inspect spark plug: Look for cracks, oil deposits, fouling, or worn electrodes.
- Swap ignition coil: Move coil 11 to another cylinder; if misfire follows, the coil is bad.
- Test injector performance: Perform injector balance testing or swap injectors.
- Inspect vacuum system: Smoke-test around intake runner for cylinder 11.
- Clean or test MAF sensor: Incorrect airflow readings can cause lean misfires.
- Review short-term and long-term fuel trims: Lean trims suggest air leaks; rich trims may indicate injector leakage.
- Measure fuel pressure: Confirm pump and regulator function.
- Perform compression test: Low compression identifies mechanical problems.
- Verify timing correlation: Cam or crank timing issues may cause intermittent misfires.
Pro Tip: On multi-cylinder engines like V10 or V12 platforms, rear cylinders such as cylinder 11 often run hotter, accelerating wear on ignition coils and spark plugs. Inspect these components very carefully.
Possible Fixes & Repair Costs
- Replace spark plug (cylinder 11): €20–€60
- Replace ignition coil: €50–€120
- Clean or replace fuel injector: €120–€260
- Repair vacuum leak: €50–€150
- Clean or replace MAF sensor: €20–€150
- Mechanical repairs (valves/piston issues): €300–€900+
Can I Still Drive With P0311?
Driving with P0311 is not recommended. A misfiring cylinder allows unburned fuel into the exhaust, which can overheat and damage the catalytic converter. If the check engine light is flashing, stop driving immediately to prevent severe damage.
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
- P0311 indicates a misfire isolated to cylinder 11.
- Most common causes include spark plug, ignition coil, injector, or vacuum issues.
- A flashing MIL warns of catalyst-damaging misfires.
- Early diagnosis reduces repair costs and protects engine components.
FAQ
What is the most common cause of P0311?
A worn spark plug or failing ignition coil on cylinder 11 is the most frequent cause.
Can a vacuum leak affect cylinder 11 only?
Yes. A localized intake runner leak can create a lean misfire specific to that cylinder.
Is it safe to keep driving with P0311?
No. Misfires can severely damage the catalytic converter and reduce vehicle performance.
How do I test the injector for cylinder 11?
Perform an injector balance test or swap injectors between cylinders to see if the misfire follows.
Should I replace all spark plugs at once?
If the plugs have high mileage, replacing all of them ensures even performance and reduces future misfires.