P0314: Single Cylinder Misfire — Cylinder Not Specified

What it means

A persistent misfire is detected on one cylinder, but the engine controller cannot identify which cylinder is affected. Often seen on engines without per-cylinder feedback or when crank position correlation fails.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The engine controller detects misfires by monitoring crankshaft speed, but its available information does not let it assign the event to a particular cylinder. P0314 indicates a single-cylinder misfire pattern without a cylinder number, so diagnosis must first identify which cylinder is weak before replacing a component.

Common causes

Most likely first.

1. Weak ignition component on one cylinder
2. Injector partially clogged
3. Low compression on one cylinder

Symptoms

• Check engine light on or flashing
• Rough idle and uneven running
• Power loss, hesitation under acceleration
• Increased fuel consumption
• Possible smell of unburned fuel from exhaust

How to diagnose it

1. Read freeze-frame data and any pending cylinder-specific misfire counts to see whether the fault is limited to one operating condition or cylinder.
2. Inspect ignition components, injector connectors, and wiring across the cylinders for obvious damage before narrowing down the source.
3. Use the scan tool’s available cylinder balance or misfire data to identify whether one cylinder contributes less than the others.
4. If a weak cylinder can be isolated, swap its interchangeable coil or plug with another cylinder and check whether the misfire moves.
5. If the misfire remains with one cylinder or cannot be isolated electrically, test injector operation and compare compression with the manufacturer’s specification.

Common fixes

• Repair damaged ignition or injector wiring found during inspection.
• Replace the worn spark plug on the cylinder identified by testing.
• Replace a weak ignition coil if the misfire follows it during a swap test.
• Clean or replace a faulty injector on the affected cylinder.
• Repair the cause of low compression if mechanical testing confirms it.

Can I keep driving?

If the check engine light flashes, stop driving when safe because an active misfire can damage the catalytic converter. With a steady light and mild symptoms, keep any trip short and gentle; the unspecified cylinder makes continued diagnosis important.