Fouled Plug Clearing Procedure

For use when you experience excessive mag drop during ground run-up on either or both mags. When taxiing or idling for long periods (like a taxi from 20L/R) please lean the mixture to prevent plug fouling.

  1. Make sure the engine is warm. There should be a positive indication on the oil temperature gauge.
  2. With the mixture full rich, increase the RPM to 2000.
  3. Lean the mixture slowly. Watch the EGT gauge to make sure it is increasing. Lean until the engine begins to run rough. Allow it to run there for 5-10 seconds.
  4. Try the mag check again.
  5. If the problem persists increase the RPM by 100 or 200, continuing to lean aggressively.
  6. Try the mag check again.
  7. If the problem persists, repeat steps 2 through 6 until the RPM drop during a mag check is 100 RPM or less, but not more than three or four times.
  8. If unable to clear the problem, report the problem as a squawk. It may be more serious than a fouled plug.
  9. To reduce the likelihood of fouled plugs, lean the engine during cruise regardless of altitude.