Acura Coupes and Sedans 1986-1993 Repair Guide

Air Injection System

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See Figure 1

The Legend uses an air injection system designed to improve emissions performance by supplying fresh air into the exhaust manifold by way of the air suction valve. When the air suction control solenoid valve is activated, manifold vacuum raises the diaphragm valve of the air suction valve. Fresh air from the air cleaner is forced into the exhaust manifold by way of the reed valve of the air suction valve, by the pulsation of the exhaust gas.



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Fig. Fig. 1: Air injection system-Legend

TESTING



Air Suction Control Solenoid Valve
  1. Start the engine and warm to normal operating temperature. Make sure the cooling fan comes ON.
  2.  
  3. Disconnect the No. 7 vacuum hose from the air suction valve and check for vacuum. If there is no vacuum, block the rear wheels and raise and safely support the front of the vehicle. If vacuum does exist, skip the next step and proceed to Step 4.
  4.  
  5. Place the transmission in 2nd gear and check for vacuum at 1500 rpm and above 9 mph. If vacuum exists, reconnect No. 7 hose and listen for air suction noise from the air suction valve at 1500 rpm and above 9 mph. If noise is heard operation is normal and air injection system is OK.
  6.  
  7. If vacuum does exist after Step 2, disconnect the 6-pin connector.
  8.  
  9. Check for vacuum and if it exists, inspect air injection system hose routing. If hose routing checks out OK, replace air suction control solenoid valve.
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  11. If vacuum does not exist after disconnecting the 6-pin connector, inspect the wiring between the 6-pin connector and the ECU. If the wiring checks out OK, substitute a known-good ECU and recheck. If the symptom goes away, replace the original ECU.
  12.  
  13. If vacuum does not exist after Step 3, turn the ignition switch OFF and disconnect the 6-pin connector. Restart the engine and measure the voltage between the BLK/YEL terminal and the GRY terminal during acceleration at 1500 rpm and above 9 mph. If there is battery voltage inspect the vacuum hose routing. If the hose routing checks out OK, replace the air suction control solenoid valve.
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  15. If there is no voltage present, measure the voltage between the BLK/YEL terminal and the body ground. If voltage does not exist, repair the wiring between the No. 22 fuse and the 6-pin connector. If voltage does exist, inspect the wiring between the 6-pin connector and the ECU. If the wiring checks out OK, substitute a known-good ECU and recheck. If the symptom goes away, replace the original ECU.
  16.  

 
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