Acura Coupes and Sedans 1986-1993 Repair Guide

Chamber Volume Control System

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On the Legend, this system helps to enhace engine power delivery at varying engine speeds. This is accomplished by the controlled opening and closing of a valve in the intake tract. The net effect is that when the valve is closed at low rpms, high torque is achieved. When the valve is opened higher rpms are achieved, thus greater performance.

INSPECTION



Legend

See Figure 1



Click image to see an enlarged view

Fig. Fig. 1: Chamber volume control system-Legend

  1. Start the engine and allow it to idle.
  2.  
  3. Remove the No. 2 vacuum hose from the bypass low control diaphragm and connect the vacuum gauge to the hose. If there is vacuum, skip to Step 3. If there is no vacuum, proceed to the next step.
    1. Disconnect the No. 4 hose to the bypass low control diaphragm and connect a vacuum gauge to the hose. If there is no vacuum, check between the vacuum tank and the manifold for a blockage or vacuum leak. If there is vacuum, disconnect the 6-pin connector.
    2.  
    3. Measure the voltage between the Black/Yellow (+) terminal and the Red/Blue (-) terminal. If there is battery voltage present, replace the bypass low control solenoid valve.
    4.  
    5. If there is no voltage, measure the voltage between the Black/Yellow terminal and the body ground. If there is no battery voltage present, check the Black/Yellow wiring between the 6 pin connector and the No. 22 fuse for a short.
    6.  
    7. If there is battery voltage, turn the ignition switch OFF and connect the test harness between the ECU and the electrical connector. Check for continuity of the Red/Blue wire between the ECU and the 6 pin connector.
    8.  
    9. If continuity exists, substitute a known good ECU and check. If the problem goes away, replace the ECU. If continuity does not exist, repair short in the wiring between the 6 pin connector and the ECU.
    10.  

  4.  
  5. Remove the No. 8 hose from the bypass high control diaphragm and connect the vacuum gauge to the hose. Check for vacuum at the tank and if there is vacuum present, skip to Step 4. If no vacuum is present, continue to Step a.
    1. Disconnect the No. 4 hose on the bypass high control solenoid valve and connect a vacuum gauge to the hose. If no vacuum is present, repair the blockage or vacuum leak between the vacuum tank and the manifold.
    2.  
    3. If there is vacuum present, disconnect the 6 pin connector and measure the voltage between the Black/Yellow (+) and the Yellow (-) terminals.
    4.  
    5. If there is battery voltage present, replace the bypass high control solenoid valve. If battery voltage is not present, measure the voltage between the Black/Yellow (+) terminal and the body ground. If there is no battery voltage, repair the open in the Black/Yellow wire between the 6-pin connector and the No. 22 (10A) fuse. If there is battery voltage present, proceed to the next step.
    6.  
    7. Turn the ignition switch OFF and connect a PGM-FI test harness between the ECU and connector.
    8.  
    9. Check if there is continuity of the Yellow wire between the ECU (A18) and the 6-pin connector. If there is no continuity, repair the Yellow wire between the ECU (A18) and the 6-pin connector. If continuity does exist, substitute a known good ECU and recheck.
    10.  

  6.  
  7. Raise the engine speed to 3300 rpm and check for vacuum at No. 2 vacuum hose.
  8.  
  9. If there is vacuum present, disconnect the 6 pin connector and check again, if vacuum still exists, replace the bypass low control solenoid valve.
  10.  
  11. If vacuum is not present, raise engine speed to 4000 rpm and check for vacuum at No. 8 vacuum hose. If vacuum is still not present, the chamber volume control system is OK.
  12.  
  13. If vacuum is present, disconnect the 6 pin connector and check again; if vacuum still exists, replace the bypass high control solenoid valve.
  14.  
  15. If vacuum does not exist, turn the ignition switch OFF and disconnect the A connector from the ECU.
  16.  
  17. Check for continuity to ground on the Yellow wire. If there is continuity, repair the short to the ground at the Yellow wire between the ECU (A18) and the 6 pin connector.
  18.  
  19. If continuity does not exist, substitute a known-good ECU and recheck.
  20.  

 
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