1979 Honda Prelude Automatic TransFACTORY OEM SERVICE PROCEDURE

1975 Models

  1. Disconnect vacuum hose from dashpot. Connect tachometer to engine. Start engine, lift dashpot arm fully, and plug vacuum port on dashpot. Engine speed should increase.
  2. Keeping vacuum port plugged, release dashpot arm. Engine speed should stabilize and maintain 2000-4000 RPM. If speed is too low, widen slot in dashpot speed adjustment lever. If speed is too high, narrow slot in dashpot speed adjustment lever.
  3. Reconnect vacuum hose and turn ignition on. Lift dashpot arm fully and release, counting time required for throttle valve to return to idle. If throttle valve does not close or takes longer than 4 seconds, replace dashpot solenoid.
  4. If throttle valve closes in less than one second, measure voltage between emission control box connector Black/Yellow wire and Black (ground) wire. If 12 volts exist, replace faulty solenoid. If no voltage exists, check wiring or fuse.
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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