P0314: Single Cylinder Misfire (Cylinder not Specified)

P0314 means the engine computer has detected repeated misfires on one cylinder but has not identified which cylinder it is. The cause is the same as for any single-cylinder misfire, most often a worn spark plug, a failing ignition coil, an injector fault, an intake leak at one cylinder or low compression; the extra work is finding the cylinder. Many engine computers name the cylinder instead, with P0301 to P0308, so check for one of those stored alongside it.

P0314 is a misfire-related diagnostic trouble code classified as high severity. When your vehicle's ECU detects this condition, it stores P0314 and illuminates the check engine light.

If your vehicle has triggered P0314, you may notice one or more of these symptoms:

• Check engine light on, or flashing while the misfire is active
• Rough or shaking idle with a regular stumble
• Vibration felt through the seat or steering wheel
• Hesitation and loss of power when accelerating
• Higher fuel consumption
• Fuel or rotten-egg smell from the exhaust

Here are the most common causes of P0314:

No - address this immediately. A misfiring cylinder sends unburned fuel into the exhaust, which can overheat and ruin the catalytic converter, and the engine can lose power at an awkward moment. If the check engine light is flashing, stop as soon as it is safe. If it is steady and the engine still runs smoothly enough, drive only the short distance to a workshop, gently and without heavy loads.

Follow these steps to pinpoint the root cause of P0314:

1. Read every stored code and the freeze frame. A cylinder-specific code such as P0301 to P0308 stored at the same time or later tells you the cylinder straight away, and the freeze frame shows the engine speed, load and temperature when the misfire happened
2. On many newer cars the Mode 06 test results, which a generic OBD2 reader can show, include a misfire count for each cylinder. The cylinder with a count far above the rest is the one to test first
3. If the misfire is happening now, listen and feel for the stumble at idle, and on engines with individual coils unplug one coil at a time with the engine idling: the cylinder whose coil makes no difference to the idle when unplugged is the one not firing. Do this briefly, because it adds unburned fuel to the exhaust
4. Remove and inspect the spark plugs. A plug that looks different from the others (wet, oily, sooty or with a worn or damaged electrode) points to its cylinder
5. Swap the suspect cylinder's coil with a neighbour, clear the codes and drive. If the misfire moves with the coil, replace the coil
6. If ignition is ruled out, check that cylinder's injector for sound and resistance, smoke-test the intake for leaks, and run a compression test to compare all cylinders
7. If no cylinder stands out and the misfire is not reproducible, check the crankshaft position sensor, its wiring and the tone wheel, because an irregular signal can be counted as a misfire

Repair costs for P0314 vary depending on the root cause and your vehicle. Here are typical estimates:

P0314 behaves differently depending on your vehicle. Select your car below for model-specific causes and known issues:

These codes are often seen alongside P0314 or indicate related issues: