Accord 1985-89 and Prelude 1986-89
1. With the engine off, slowly open the throttle until the damper link is fully up.
2. Release the throttle and note the time it takes for the throttle to touch the stop screw. This time must be less than two seconds.
3. If this time is more than two seconds, replace the damper control valve.
4. If the draft does not function - check the feedback or clogging of the control valve or vacuum line. If everything is in order, replace the air damper.
Accord 1987-89
1. Check the vacuum line for leaks, blockages, or accidental hose disconnections.
2. Disconnect the No. 6 vacuum hose from the air damper diaphragm and connect a hand pump with a pressure gauge to the free end of the hose.
3. Start the engine.
4. Increase the engine speed to 3500 rpm. The gauge should show vacuum.
5. If there is no vacuum, check the vacuum pipe on the throttle.
6. Release throttle. The vacuum should slowly disappear.
7. If the vacuum holds or disappears quickly, replace the damper control valve.
8. Connect the vacuum pump to the damper diaphragm.
9. Apply vacuum and check that the rod has moved and the vacuum is being held.
10. If the vacuum is not being held or the linkage is not moving, replace the damper diaphragm.