1977-79 Models

Warm engine to normal operating temperature. Run engine at 2000 RPM for 3 minutes. Turn off all accessories. Unhook and plug idle compensator hose. Remove fuel filler cap. Connect exhaust gas analyzer to exhaust pipe and tachometer to engine.
With manual transmission in Neutral or automatic transmission in Drive, turn air adjustment screw (located on carburetor body, above mixture screw) to obtain specified idle speed. If CO% level is within specifications and idle speed is stable, mixture adjustment is not required.
If CO% level is not within specifications, remove idle limiter cap from mixture adjusting screw. Turn screw clockwise until idle speed begins to fluctuate.
Slowly turn mixture adjusting screw counterclockwise until maximum specified CO% level is obtained, then turn mixture screw an additional 1/2 turn counterclockwise. Recheck idle speed and readjust if necessary. Replace idle mixture limiter cap and restore all components to original positions.

Fig 1: Typical Ignition Timing Adjustment Points
Courtesy of MAZDA MOTORS CORP.

IDLE SPEED & CO% LEVEL SPECIFICATIONS