1986 Honda Prelude Base, AutomaticFACTORY OEM SERVICE PROCEDURE

System Testing

  1. Ensure engine is at operating temperature. Remove air cleaner cover and filter element. Disconnect hose from main air jet solenoid valve and install vacuum pump to solenoid valve. Start engine and apply vacuum at idle. If there is no vacuum present, proceed to step 4).
  2. If there is vacuum, check for voltage at main air jet solenoid valve. If there is no voltage, replace solenoid valve and retest. If there is voltage, check the following:
  3. Check speed sensor (auto. trans. only), intake air temperature sensor and vacuum switch A. Check for voltage at control unit connector (Black/Yellow wire) with ignition on. There should be voltage. If there is no voltage, check wiring. Ensure Brown/Black wire between control unit and ground has continuity.
  4. Disconnect vacuum hose No. 2 from control box No. 1. Apply vacuum with engine at idle. If vacuum remains steady, disconnect vacuum gauge and reconnect air hoses and air cleaner. If there is no vacuum, check for voltage at main air jet solenoid valve.
  5. If there is voltage, replace the solenoid valve and retest. If there is no voltage, check the following: speed sensor (auto. trans. only), intake air temperature sensor and vacuum switch A. Check for voltage at control unit connector (Black/Yellow wire) with ignition on.
  6. There should be voltage. If there is no voltage, check wiring. Ensure Brown/Black wire between control unit and ground has continuity.
Fig 1: Main Air Jet Control System
G36678
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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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