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Pulse Air System Honda Prelude III

Testing & Diagnostics 2 illustrations ~1132 words

DESCRIPTION

All carbureted models are equipped with a Pulse Air System (also called Secondary Air Supply System). This system uses vacuum pulses in the exhaust manifold to draw air from the air cleaner to the exhaust manifold.

OPERATION

When vehicle exceeds set speed of speed sensor and manifold vacuum is above set vacuum of control switch, control switch solenoid valve and control switch are open. The control unit energizes the air suction control solenoid valve, applying manifold vacuum to air suction cut-off diaphragm valve. This will in turn open secondary air passage.

When vacuum, induced by pulsation in exhaust manifold, makes air suction reed valve open, fresh air enters exhaust manifold. The control switch bellows adjust their operation in response to atmospheric pressure. Air chambers act as silencers to reduce exhaust noise.

Scheme 19

Scheme 19: OPERATION
Scheme 19: OPERATION

CONTROL UNIT CONNECTOR

  1. Turn ignition on and check for voltage at control unit connector (Blue wire). Voltage should be present. If there is no voltage, check Blue wire between ignition coil and control unit.
  2. Turn ignition on and check for voltage at Black/Yellow wire. If there is no voltage, check wiring. Check Brown/Black wire for continuity between electronic control unit and ground. Continuity should be present.

INTAKE AIR TEMPERATURE SENSOR

Unplug air intake temperature sensor connector. Check for continuity when air temperature is below 40°F (4.5°C). Check for lack of continuity when air temperature is above 73°F (23°C). Replace sensor if sensor does not test as specified.

SPEED SENSOR

  1. Raise and support front of vehicle. Set parking brake and block rear wheels. Back probe voltmeter or test light positive probe into Yellow/Black wire terminal at control unit connector.
  2. Connect negative probe to ground. Start engine. Place vehicle in second position (gear selector in 2 position for auto. trans.) and accelerate slowly. Battery voltage should be as indicated in SPEED SENSOR VOLTAGE CHECK table. SPEED SENSOR VOLTAGE CHECK Speed Voltage Below 11 MPH Yes Above 16 MPH No
  3. If voltmeter readings do not correspond to above MPH ranges, install new speed sensor and retest. If voltage was not present during step 2), check for bad electrical connection, fuse or faulty speed sensor. Replace or repair as necessary and retest.

THERMOSENSOR

  1. Ensure engine coolant temperature is below 104°F (40°C). Disconnect vacuum hose No. 19 from charcoal canister. If no vacuum is present at idle, thermovalve is open and test may be performed.
  2. Unplug connector at control unit. Check for resistance between Blue/Yellow and Brown/Black terminals. Resistance should be above 1000 ohms. Run engine until cooling fan comes on and check resistance again. Resistance should be about 200 ohms.
  3. If resistance is outside specified ranges, replace thermosensor and retest. If ohmmeter shows no continuity, check wires. If no defects are found, replace thermosensor and retest.

VACUUM SWITCH A

  1. Disconnect vacuum hose No. 2 to control box at vacuum hose manifold. Connect hand vacuum pump to hose. Check for continuity between Black/Yellow and Brown/White terminals of control box connector.
  2. Apply more than 4 in. Hg. Continuity should not be present. If continuity is present, replace vacuum switch A. Release vacuum. Continuity should be present. If not, replace vacuum switch A.

VACUUM SWITCH C

  1. Disconnect vacuum hose No. 15 to vacuum switch C and connect hand vacuum pump to hose. Apply 12 in. Hg to switch. Check for continuity between Black/Yellow and Blue/Black wire terminals of control box 6P connector.
  2. Continuity should be present when more than 12 in. Hg is applied, and no continuity when vacuum is released.

Scheme 20

Scheme 20: SYSTEM TESTING
Scheme 20: SYSTEM TESTING

COLD ENGINE

  1. Disconnect and plug lower air suction hose from anti-afterburn valve. Remove air cleaner cover and filter. Start engine and check for bubbling noise at air suction port during idle. If bubbling noise is not heard, proceed to step 5).
  2. If bubbling noise is heard, check for voltage at air suction control solenoid valve (Yellow/Green wire). If voltage is present, turn ignition on and check for voltage at control unit connector (Blue wire). Voltage should be present.
  3. If there is no voltage, check Blue wire between ignition coil and control unit. Check 15 MPH speed sensor, thermosensor, intake air temperature sensor, vacuum switch A and vacuum switch C. Turn ignition on and check for voltage at control unit connector (Black/Yellow wire).
  4. If there is no voltage, check wiring. Check Brown/Black wire for continuity between control unit and ground. Continuity should be present.
  5. If bubbling noise is not heard, disconnect vacuum hose No. 5 from air suction cut-off diaphragm. If vacuum is present, replace air suction control solenoid valve and retest. If there is no vacuum, replace air suction cut-off diaphragm and retest.
  6. Ensure engine coolant is below 95°F (35°C) for Calif. models or 122°F (50°C) for Federal models. Unplug intake air temperature switch connector. Check for bubbling noise at idle. If noise is heard, see «HOT ENGINE»(/honda/prelude/iii-1986-1989/remont/testing-diagnostics/#pulse-air-system__hot-engine) test.
  7. If bubbling noise is not heard, check for voltage at air suction control solenoid valve (Yellow/Green wire). If voltage is not present, turn ignition on and check for voltage at control unit connector (Blue wire). Voltage should be present.
  8. If there is no voltage, check Blue wire between ignition coil and control unit. Check 15 MPH speed sensor, thermosensor, intake air temperature sensor, vacuum switch A and vacuum switch C. Turn ignition on and check for voltage at control unit connector (Black/Yellow wire).
  9. If there is no voltage, check wiring. Check Brown/Black wire for continuity between control unit and ground. Continuity should be present. If there is voltage, replace air suction control valve and retest.

HOT ENGINE

  1. Disconnect and plug lower air suction hose from anti-afterburn valve. Remove air cleaner cover and filter. Raise and support front of vehicle. Set parking brake and block rear wheels.
  2. Place shift lever in second position (selector lever in "2" position for auto. trans.) and accelerate above 15 MPH. Quickly release throttle and check for bubbling noise. If bubbling noise is heard, system is okay.
  3. If bubbling noise is not heard, check for voltage at air suction control solenoid valve (Yellow/Green wire). If voltage is not present, turn ignition on and check for voltage at control unit connector (Blue wire). Voltage should be present.
  4. If voltage is not present, check Blue wire between ignition coil and control unit. Check speed sensor, thermosensor, intake air temperature sensor, vacuum switch A and vacuum switch C. Turn ignition on and check for voltage at control unit connector (Black/Yellow wire).
  5. If there is no voltage, check wiring. Check Brown/Black wire for continuity between control unit and ground. Continuity should be present.
  6. If there is voltage, disconnect vacuum hose No. 5 from air suction cut-off diaphragm. Check for disconnected or leaking vacuum hoses. If okay, replace air suction cut-off diaphragm valve and retest. If vacuum is present, replace air suction cut-off diaphragm and retest.

See also:
• HOT ENGINE

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