The ACV is designed to control air injected from the air pump and direct it to either the main cat or bypass to a noise muffler in the front passenger corner of the front bumper.  Within the ACV is the anti-burn valve that is supposed to suppress backfires in the exhaust system.  A malfuncitoning ACV can cause emission problems, and a replacement can only be bought from a Mazda dealer.  Without a properly functioning ACV, it's almost impossible to pass almost any emissions testing.

Questions?  Comments?  Send mail to: