1977 Mazda Cosmo Automatic TransFACTORY OEM SERVICE PROCEDURE

1975 Models

  1. Turn ignition on. Unplug connector at both solenoids. A "clicking" sound should be heard from both solenoids when disconnected. If not, replace solenoid(s).
  2. Connect tachometer to engine. Start and run engine at idle. Disconnect air hose from deceleration control valve at air cleaner. Block air hose opening with hand. See Figure. Engine speed should not change noticeably.
  3. Block air hose opening with hand. Rapidly accelerate engine to 4000 RPM and quickly release throttle. Vacuum should be felt at end of hose for 1-1 1/2 seconds, tapering off until engine reaches 1150 RPM.
    NOTE: On manual transmission equipped vehicles, only a small amount of vacuum may be noted.
  4. On manual transmission equipped vehicles, disconnect coasting valve solenoid and apply 12 volts to terminal. Disconnect idle switch and connect a voltmeter to power lead of coasting valve solenoid.
  5. Slowly decrease engine speed from 2000 RPM and record RPM at which current starts to flow. Current should start to flow at 1050-1250 RPM and continue to flow until idle speed is reached. Slowly increase engine speed and record RPM at which current stops flowing. Speed should be within 80-220 RPM of current flow RPM.
Factory Service Tools

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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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