Ignition

P0311 — Cylinder 11 Misfire Detected

Severity: medium Drive with care, to a shop

What P0311 means

The engine control unit watches crankshaft speed and notices when cylinder 11 contributes less acceleration than the others. That means the air-fuel mixture in that cylinder is burning poorly or not at all. This code applies to engines with 11 or more cylinders (typically V12s). Normal combustion needs spark, the right amount of fuel, air and good compression.

Symptoms

  • Check engine light on or flashing
  • Rough idle
  • Vibration at idle
  • Hesitation or stumbling under load
  • Loss of power
  • Higher fuel consumption
  • Often set along with P0300

Possible causes

  1. Worn or faulty spark plug in cylinder 11
  2. Failed ignition coil on cylinder 11 or a bad coil connector
  3. Clogged or failing fuel injector on cylinder 11
  4. Vacuum leak near that cylinder's intake runner
  5. Low compression: valve, rings or head gasket
  6. Damaged wiring or poor connector contact
  7. Rarely, a control unit fault

How to diagnose

  1. Read all codes and freeze frame data: note the conditions of the misfire and any P0300 or other cylinder codes
  2. Check per-cylinder misfire counters if your scan tool supports them
  3. Inspect the cylinder 11 plug and coil for carbon, cracks, oil or arc tracks
  4. Swap the coil (and the plug if needed) with a good cylinder, clear the code and see if the misfire follows
  5. Inspect the coil and injector connectors and wiring, and test the circuit if needed
  6. Test the injector: resistance, clicking, cylinder balance
  7. Check the intake for vacuum leaks, hoses and gaskets
  8. Run a compression or cylinder leak-down test on cylinder 11

Common fixes

  • Replace spark plugs, preferably as a full set
  • Replace the cylinder 11 ignition coil
  • Clean or replace the cylinder 11 injector
  • Fix vacuum leaks and replace damaged gaskets or hoses
  • Repair the wiring or connector
  • Do the engine mechanical repair if compression is low

Questions and answers

Can I drive with a P0311 code?

Only briefly and gently to get to a shop. If the check engine light is flashing, don't drive, since misfires can quickly damage the catalytic converter.

What most often causes P0311?

A worn spark plug or a failed ignition coil on cylinder 11 is the most common cause. If both are fine, check the injector, vacuum leaks and compression.

Why does P0311 appear on an engine with fewer cylinders?

It is most likely a scan tool misread, a wrong vehicle profile or a control unit glitch. Recheck with another scanner and review any other stored codes.

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.