Air Injection: Testing and Inspection

NOTE: Intake air temperature should be below the set temperature of the intake air temperature switch. Switch should have continuity.
1. Disconnect air suction hose from anti-afterburn valve and plug hose.
2. Remove air cleaner cover and filter.
3. Start engine and check for bubbling noise from air suction port at idle. A bubbling noise should not be heard.
4. If a bubbling noise is not heard, proceed to step 6. If bubbling noise is heard, check for voltage at the yellow/green wire of the air suction control solenoid valve.
5. If voltage is not present, proceed to step 6. If voltage is present, refer to "TROUBLESHOOTING 1984-86 Prelude."
6. Disconnect vacuum hose No. 5 from the air suction cut-off diaphragm, then connect suitable vacuum gauge to the disconnected hose and check vacuum.
7. If vacuum is present, replace air suction control solenoid valve. If vacuum is not present, replace air suction cut-off diaphragm.
8. Disconnect intake air temperature switch electrical connector, then check for bubbling noise from the air suction port at idle.

NOTE: Ensure engine coolant temperature is below 122 degrees F on models except Calif. or 95 degrees F on Calif. models.

9. If a bubbling noise is heard, proceed to step 11. If a bubbling noise is not heard, check for voltage at the yellow/green wire of the air suction control solenoid valve.
10. If voltage is present, replace air suction control solenoid valve. If voltage is not present, refer to "troubleshooting, 1984-86 Prelude."
11. Allow engine to reach normal operating temperature, then raise and support front of vehicle.
12. Place shift or selector lever in second or No. 2 position and accelerate above 15 mph, then release the throttle and check for a bubbling noise from the air suction port at idle.

NOTE: Check for bubbling noise within three minutes after releasing throttle or bubbling noise will stop automatically.

13. If a bubbling noise is heard, test is complete. If a bubbling noise is not heard, check for voltage at yellow/green wire of the air suction control solenoid valve.
14. If voltage is not present, refer to "TROUBLESHOOTING 1984 Prelude." If voltage is present, disconnect vacuum hose No. 5 from air cut-off diaphragm.
15. If vacuum is not present, check for leaks or disconnected hose. If satisfactory, replace air suction control solenoid valve. If vacuum is present, replace air suction cut-off diaphragm.

TROUBLESHOOTING 1984 PRELUDE

1. On 1984 models, inspect control switch as follows:
a. Push voltmeter positive probe into gray wire terminal at connector of emissions control box No. 1 and connect negative probe to suitable ground.
b. Start engine and check for voltage during deceleration.
c. If there is no voltage, disconnect vacuum hose No. 2 from emission control box No. 1 and check for vacuum.
d. If there is no voltage, check for leaks, blockage, or disconnected hose, correct as necessary, and repeat test.
e. If there is vacuum, check vacuum line for leaks in emissions control box No. 1.
f. If vacuum line is satisfactory, replace control switch and repeat test.
2. turn ignition switch on and check for voltage at blue wire at control unit connector. If there is no voltage, check blue wire between ignition coil and control unit.
3. On 1984 models, test air suction vacuum switch as follows:
a. Disconnect vacuum hose to vacuum switch and connect vacuum pump to hose.
b. Apply vacuum to vacuum switch and check for voltage at vacuum switch.
c. Voltage should be available under conditions sown, Fig. 72.
d. If there is no voltage, replace vacuum switch and repeat test.
4. Test or 15 mph speed sensor as outlined under "Speed Sensor, Test" procedure.
5. Test thermosensor as follows:
a. Ensure that engine is cold by disconnecting vacuum hose No. 19 at charcoal canister. There must be no vacuum at idle.
b. Disconnect connector at control unit.
c. Check resistance between blue/yellow and white/black terminals on 1983-84 models or blue/yellow and brown/black terminals on 1985-86 models. Resistance should be above 1k ohm.
d. Run engine until it reaches normal operating temperature, then check resistance again. Resistance should be approximately 200 ohms.
e. If resistance is not within specifications, replace thermosensor and repeat test.
f. If ohmmeter shows no continuity, check wires.
g. If wires are satisfactory, replace thermosensor and repeat test.
6. Turn ignition switch on and check for voltage at black/yellow wire at control unit connector. If there is no voltage, check wiring.
7. Check black or brown/black wire for continuity between control unit and suitable ground. There should be no continuity.
8. On 1984 models, test intake air temperature switch as follows:
a. Disconnect intake air temperature switch electrical connector, then check continuity between terminals.
b. Continuity should not be present if air temperature is above 73 degrees F. Continuity should be present if air temperature is below 40 degrees F. Replace sensor as required.
9. On 1984 models, inspect vacuum switches for proper operation.
10. If no faults are found in steps 1 through 9, replace control unit and repeat test.