Ignition

P0314 — Single Cylinder Misfire (Cylinder Not Specified)

Severity: medium Drive with care, to a shop

What P0314 means

The engine computer watches crankshaft speed variations and notices that one cylinder is contributing less than the others or not at all. P0314 means a misfire was confirmed in a single cylinder, but the ECM could not identify which one, so no specific P030X code was set. The cause is usually in the spark, fuel delivery or air/fuel mixture.

Symptoms

  • Check Engine light on or flashing
  • Rough or uneven idle
  • Hesitation or stumbling when accelerating
  • Loss of power, especially under load
  • Worse fuel economy
  • Higher emissions or a fuel smell from the exhaust

Possible causes

  1. Worn or fouled spark plugs
  2. Failing ignition coil or spark plug wire
  3. Clogged or leaking fuel injector
  4. Vacuum leak in the intake system, such as cracked hoses
  5. Crankshaft or camshaft sensor signal problems or damaged wiring
  6. Low compression or an internal engine problem such as valves or piston rings

How to diagnose

  1. Read all codes and freeze frame data to see when the misfire occurs
  2. Check per-cylinder misfire counters with a scan tool; one cylinder may stand out
  3. Inspect spark plugs for wear, deposits, oil or cracked insulators
  4. Swap coils and plugs between cylinders and see whether the misfire follows
  5. Test injector operation and cylinder balance, and measure fuel pressure
  6. Look for vacuum leaks: hoses, intake gasket, smoke test
  7. Check crankshaft and camshaft sensors and their wiring connectors
  8. Run a compression or leak-down test

Common fixes

  • Replace spark plugs as a set
  • Replace the faulty ignition coil or wires
  • Clean or replace injectors and fix fuel pressure problems
  • Repair vacuum leaks and replace damaged hoses or gaskets
  • Repair wiring or replace a faulty position sensor
  • Perform engine mechanical repairs if compression is low

Questions and answers

How is P0314 different from P0301–P0308?

P0301–P0308 point to a specific cylinder. P0314 says one cylinder is misfiring but the ECM could not tell which. You have to narrow it down with misfire counters and part swapping.

Can I drive with P0314?

Only briefly and under light load if the light is steady. If the light is flashing, avoid driving because the catalytic converter can be damaged quickly.

Where should I start the repair?

Start with spark plugs and ignition coils, the most common causes. Then check the injectors and look for vacuum leaks.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.