← Mazda Miata NB (1999-2005 US model years) problems

EGR codes and idle drop

Limited · Severity: Low · Years: 1999-2000 (listed)

Symptoms

EGR codes 0401/0402, idle dips at a stop.

Cause

Listed as common on the year-by-year page only (search excerpt).

Fix (summary)

The forum mentions an updated plug choice and an off-computer idle adjustment as ideas; unverified.

Sources

• Miata problems/maintenance by year — miatayear.com (editorial; read 2026-10-15; search excerpt only)
• Common Issues with NB 1998-2005 Miatas — MX-5 Miata Forum (forum thread; read 2026-10-15; search excerpt only)

Summaries are in our own words. Not repair instructions; consult the factory service manual.