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Air Injection System Honda Prelude II

Testing & Diagnostics 2 illustrations ~1092 words

DESCRIPTION

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

OPERATION

When vehicle exceeds set speed of speed sensor and manifold vacuum is above set vacuum of control switch, the control switch solenoid valve and control switch are open. The control unit energizes the air suction control solenoid valve to apply manifold vacuum to the air suction cut-off diaphragm valve, which opens the 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.

Pulse Air System. Scheme 12

Scheme 12: Pulse Air System
Scheme 12: Pulse Air System

CONTROL UNIT CONNECTOR

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

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 the negative probe to ground. Start engine. Place vehicle in second position (gear selector in 2 position) and accelerate slowly. Battery voltage should be as shown 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 a new speed sensor and retest. If there was no voltage 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 there is no vacuum at idle, thermovalve is open and test may be performed.
  2. Disconnect 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 ranges, replace thermosensor and retest. If ohmmeter shows no continuity, check wires. If there are no defects, replace thermosensor and retest.

VACUUM SWITCH A

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

VACUUM SWITCH C

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

Air Suction Port Location. Scheme 13

Scheme 13: Air Suction Port Location
Scheme 13: Air Suction Port Location

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 at idle. If a 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 there is voltage, check for voltage at control unit connector (Blue wire) with ignition on. There should be voltage.
  3. If 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. Check for voltage at control unit connector (Black/Yellow wire) with ignition on.
  4. There should be voltage. If no voltage, check wiring. Check Brown/Black wire for continuity between control unit and ground. There should be continuity.
  5. If bubbling noise is not heard, disconnect vacuum hose No. 5 from air suction cut-off diaphragm. If there is vacuum, replace air suction control solenoid valve and retest. If 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. Disconnect intake air temperature switch connector. Check for a bubbling noise at idle. If noise is heard, see «HOT ENGINE»(/honda/prelude/ii-1983-1987/remont/testing-diagnostics/#air-injection-system__hot-engine) test.
  7. If bubbling noise is not heard, check for voltage at air suction control solenoid valve (Yellow/Green wire). If there is no voltage, check for voltage at control unit connector (Blue wire) with ignition on. There should be voltage.
  8. If 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. Check for voltage at control unit connector (Black/Yellow wire) with ignition on.
  9. There should be voltage. If no voltage, check wiring. Check Brown/Black wire for continuity between control unit and ground. There should be continuity. If there is voltage, replace air suction control valve and retest.

HOT ENGINE

  1. Disconnect and plug the 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) 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 there is no voltage, check for voltage at control unit connector (Blue wire) with ignition on. There should be voltage.
  4. If no voltage, check Blue wire between ignition coil and control unit. Check speed sensor, thermosensor, intake air temperature sensor, vacuum switch A and vacuum switch C. Check for voltage at control unit connector (Black/Yellow wire) with ignition on.
  5. There should be voltage. If no voltage, check wiring. Check Brown/Black wire for continuity between control unit and ground. There should be continuity.
  6. If there is voltage, disconnect vacuum hose No. 5 from air suction cut-off diaphragm. Check vacuum hose for leaks or disconnected. If okay, replace air suction cut-off diaphragm valve and retest. If there is vacuum, replace air suction cut-off diaphragm and retest.

See also:
• HOT ENGINE

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