1978 Mazda Cosmo Automatic TransFACTORY OEM SERVICE PROCEDURE

1974 Models

  1. Disconnect hose from air cleaner-to-deceleration control valve (at valve). See Fig 1. With engine at idle, ensure there is no vacuum at control valve port. Stop engine.
  2. Disconnect hose from air cleaner-to-coasting valve and plug vacuum port of deceleration control valve. With engine at idle, disconnect solenoid wire from anti-afterburn valve. Hold hand over suction hose of anti-afterburn valve, no suction should be felt.
  3. Stop engine. Reconnect solenoid wire and hose to deceleration control valve. Disconnect hose from intake manifold at anti-afterburn valve and plug air suction port.
  4. With engine at idle, disconnect wire from coasting valve solenoid. Hold hand over opening of air suction hose of deceleration control valve. Vacuum should be felt. Reconnect all hose and wires.
Fig 1: 1974 Deceleration Control Valve
G09310008Courtesy of MAZDA MOTORS CORP.
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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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