1977 Mazda Cosmo Automatic TransFACTORY OEM SERVICE PROCEDURE

1976-77 California Models

  1. Connect tachometer and timing light to trailing spark plug wire (topmost spark plug). Disconnect water temperature switch and connect a jumper wire to both connector terminals. See Figure.
  2. Start engine and set engine speed at 2000 RPM with choke knob. Slowly accelerate engine. Timing light should flash at 4200-5000 RPM. Push choke knob in and return engine to idle speed.
  3. Slowly increase engine speed. When engine speed reaches 3600-4400 RPM, pull choke knob out. Timing light should flash for about 104-156 seconds. After 156 seconds, push choke knob in and return engine to idle speed.
    Fig 1: 1977-78 Ignition Timing Control System (California Cosmo & RX4 With Manual Transmission Shown)
    G09310037Courtesy of MAZDA MOTORS CORP.
  4. Slowly increase engine speed again. Timing light should flash at 2700-3300 RPM (2300-2700 RPM with automatic transmission). Return engine to idle speed.
  5. Slowly increase engine speed to 2000 RPM and allow engine speed to slowly decrease. Timing light should flash at 1050-1250 RPM. Return engine to idle speed.
  6. Slowly increase engine speed again. Timing light should stop flashing within 100-200 RPM of speed recorded in step 5)  . Increase engine speed to 2000 RPM. Timing light should flash when idle switch lever is pushed completely toward idle position.
  7. On manual transmission equipped vehicles, set engine speed to 2000 RPM and depress clutch pedal. Timing light should flash when shifting into 5th gear. Return transmission to Neutral.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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