P0311 – Cylinder 11 Misfire Detected

Last updated: April 4, 2026

DTC P0311 is an ISO/SAE controlled, General powertrain code that indicates the engine control module has detected a misfire specifically attributed to cylinder 11. A misfire means cylinder 11 is not contributing power consistently, which can lead to rough running, hesitation, and increased emissions. The control module identifies misfires by monitoring crankshaft speed variations; when combustion in a cylinder is weak or absent, the crankshaft does not accelerate as expected during that cylinder’s firing event. P0311 identifies the affected cylinder number, not the failed component, so accurate testing is required to determine whether the root cause is ignition, fuel delivery, air/fuel mixture, wiring, or an internal mechanical problem affecting cylinder 11.

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P0311 Quick Answer

P0311 – Cylinder 11 Misfire Detected means the control module has detected misfire events assigned to cylinder 11; confirm the misfire with scan data, then test ignition, fuel, air/leak influences, wiring integrity, and cylinder 11 mechanical condition before replacing parts.

What Does P0311 Mean?

P0311 is defined as Cylinder 11 Misfire Detected. In practical terms, the engine control module has determined that cylinder 11 is not producing torque as consistently as expected. This can be felt as a rough idle, stumble, or loss of power, but the code can also set when the misfire is mild and only occurs under certain operating conditions.

Importantly, P0311 is a cylinder identification code, not a component identification code. It does not, by itself, prove a failed spark plug, ignition coil, fuel injector, or mechanical defect. It only confirms that misfire monitoring logic has associated abnormal crankshaft speed behavior with cylinder 11.

Theory of Operation

The misfire monitor works by using crankshaft position information to evaluate tiny changes in rotational speed. During normal operation, each cylinder’s combustion event produces a predictable increase in crankshaft speed. The control module correlates those acceleration patterns to the engine’s firing order and cylinder positions, allowing it to “assign” a misfire to a particular cylinder when a contribution is missing or reduced.

P0311 sets when the control module detects misfire activity that meets its enable criteria and threshold and can be attributed to cylinder 11. Because crankshaft speed fluctuation is the shared symptom of many different faults, the diagnostic approach must consider ignition energy, correct fueling, unwanted air (vacuum/intake leaks), electrical supply and control integrity, and cylinder 11 compression/sealing and valve timing factors.

Symptoms

• Illuminated malfunction indicator lamp (MIL); it may flash if the misfire rate is high enough
• Rough idle or uneven engine vibration
• Hesitation, stumble, or surging during acceleration
• Reduced engine power, especially under load
• Intermittent bucking or shaking at certain RPM ranges
• Possible fuel odor from the exhaust when misfire is severe
• Hard starting or unstable idle immediately after start in some conditions

Common Causes

• Worn, fouled, damaged, or incorrectly gapped spark plug at cylinder 11
• Ignition coil, coil boot, or related high-voltage insulation breakdown affecting cylinder 11
• Poor electrical connection at the cylinder 11 ignition coil or fuel injector (corrosion, loose terminals, damaged locks)
• Wiring faults in cylinder 11 ignition or injector circuits (open, short, chafing, heat damage)
• Fuel injector fault on cylinder 11 (restricted flow, intermittent operation, or electrical failure)
• Unmetered air/vacuum leak influencing cylinder 11 air/fuel mixture (for example near the intake runner or related sealing points)
• Fuel delivery problems that contribute to a lean condition under certain loads (pressure/volume concerns)
• Mechanical condition issues on cylinder 11 (low compression, leakage, valve sealing concerns, or related mechanical contributors)

Diagnosis Steps

Tools needed: Scan tool capable of reading freeze-frame data and misfire data (including Mode $06 if available), digital volt/ohm meter (DVOM), basic hand tools for ignition component access, and a compression gauge. Depending on access and results, a noid light or oscilloscope can help verify injector control, and a leak-down tester can help confirm mechanical leakage.

1. Confirm the code and capture data: Verify P0311 is present (pending, stored, or confirmed). Record freeze-frame data (RPM, load, coolant temperature, fuel system status, and fuel trims) so you can recreate the conditions under which the misfire was detected.
2. Check for related DTCs: Look for additional misfire codes, fuel trim codes, circuit codes (injector/coil), or other powertrain codes that may change your diagnostic path. Address codes that indicate a shared power/ground or control issue before focusing only on cylinder 11 parts.
3. Identify cylinder 11 correctly: Use reliable service information for cylinder numbering and bank orientation. Ensure you are testing the actual cylinder 11 ignition and injector components, not an adjacent cylinder due to numbering confusion.
4. Review misfire data: Use the scan tool to view cylinder-specific misfire information (misfire counters and/or Mode $06 results if supported). Note whether the misfire is primarily at idle, under load, during acceleration, or at a specific RPM range.
5. Perform a focused visual inspection: Inspect cylinder 11 ignition components (coil housing, boot, and plug well) for oil contamination, moisture, carbon tracking, torn boots, or damage. Inspect injector and coil connectors for corrosion, broken locks, pushed-back pins, and poor terminal tension. Check harness routing for rub-through, heat exposure, or contact with sharp edges.
6. Check ignition on cylinder 11: Remove and inspect the spark plug from cylinder 11 for wear, fouling, cracking, or improper gap. If applicable, inspect the coil boot and spring/contact. If misfire data suggests ignition sensitivity (worse under load), prioritize verifying strong ignition performance on cylinder 11.
7. Use controlled swap testing when appropriate: If access allows and no wiring damage is found, swap the cylinder 11 ignition coil with another cylinder and retest. If the misfire follows the swapped coil, that supports an ignition coil/boot-related fault. If it does not move, continue testing rather than replacing parts based solely on suspicion.
8. Verify injector power and control: Check for proper supply voltage at the injector with key on (as applicable) and verify the control side can pulse the injector using an appropriate test method (such as a noid light or scope). Confirm connector integrity and wiring condition to rule out an electrical issue that can mimic a bad injector.
9. Evaluate mixture and fuel delivery influence: Review short- and long-term fuel trims under the freeze-frame conditions and during the misfire event. If data suggests a lean condition, inspect for unmetered air and verify fuel pressure/volume as needed. If data suggests overly rich operation on that cylinder, consider injector leakage or other contributors supported by test results.
10. Confirm mechanical integrity of cylinder 11: If ignition and injector checks do not identify the fault, perform a compression test on cylinder 11 and compare against other cylinders. If compression is low or inconsistent, follow with a leak-down test to identify leakage paths. Mechanical issues can cause repeatable misfires that will not “move” with component swaps.

Professional tip: When electrical faults are suspected, favor voltage-drop testing under load over simple resistance checks. A circuit can measure “good” with an ohmmeter but still fail under heat, vibration, or current demand, causing intermittent misfire detection on cylinder 11.

Possible Fixes

• Replace the spark plug on cylinder 11 if inspection shows wear, fouling, damage, or incorrect gap
• Repair or replace the ignition coil/boot on cylinder 11 if testing shows the misfire follows the component or if insulation breakdown is confirmed
• Repair poor electrical connections at the cylinder 11 ignition coil or injector (terminal tension, corrosion, damaged connector locks)
• Repair wiring faults affecting cylinder 11 ignition or injector circuits (opens, shorts, chafing, heat damage)
• Service or replace the cylinder 11 fuel injector if testing confirms an injector electrical or flow-related fault
• Repair vacuum/intake leaks that can skew cylinder 11 air/fuel ratio
• Address mechanical issues on cylinder 11 if compression/leak-down results confirm a sealing or internal condition problem

Can I Still Drive With P0311?

Driving with P0311 is not recommended if the engine is running rough, the MIL is flashing, or power delivery is unreliable. A persistent misfire can increase emissions and can overheat the catalytic converter if unburned fuel enters the exhaust. If the vehicle shakes heavily, hesitates during acceleration, or the MIL flashes, reduce load immediately and have the issue diagnosed before further driving. If the engine feels smooth and the MIL is not flashing, limited driving may be possible, but the correct approach is to diagnose and correct the cylinder 11 misfire as soon as possible.

How Serious Is This Code?

P0311 can range from moderate to severe depending on misfire frequency and operating conditions. Even an intermittent cylinder 11 misfire can reduce performance and increase emissions. A frequent or sustained misfire can create drivability and safety concerns (hesitation during merges or unstable idle) and can contribute to catalytic converter overheating when misfire rates are high. Because the code identifies a misfire on a specific cylinder, prompt diagnosis is important to prevent extended operation with an ongoing combustion fault.

Common Misdiagnoses

A frequent misdiagnosis is replacing ignition parts on cylinder 11 without verifying the misfire follows the component or without confirming power/ground/control integrity at the coil or injector. Another error is testing the wrong cylinder due to incorrect cylinder numbering, especially on engines with many cylinders. It is also easy to overlook vacuum/intake leak influence or mechanical compression problems when the symptom feels like “ignition.” Accurate diagnosis requires confirming cylinder 11 location, using scan data to understand when the misfire occurs, and validating ignition, injector control, and mechanical condition with tests rather than assumptions.

Most Likely Fix

The most likely fix is the repair that restores consistent combustion on cylinder 11 after testing confirms the root cause—often correcting an ignition or fuel delivery problem on that cylinder (such as a verified spark plug or ignition coil/boot issue, a confirmed injector fault, or an electrical connection/wiring repair). If ignition and fuel checks pass, compression and leak-down testing may identify a mechanical cause that must be addressed to eliminate the cylinder 11 misfire.

Repair Costs

Repair cost depends on whether the confirmed root cause is wiring, connector condition, a sensor, a module, or the labor needed to diagnose the fault correctly.