Fails emission test (MIL works OK, no DTCs set)
Diagnostic procedure
Except FO, KE, KG, KQ, KU models: Inspect the three way catalytic converter (TWC).
Except FO, KE, KG, KQ, KU models: Check the spark plugs.
Test the fuel pressure.
Except FO, KE, KG, KQ, KU models: Test the injectors.
Check the EVAP system.
Troubleshoot the VTEC system oil pressure.
Also check for
Fuel contamination
Low compression
Broken cam chain