'87 Subaru GL Vacuum Line to Air Cleaner and Quality of Engine Idle

[sunflowersubaru]

EA82 engine idles rough.

 

In checking vacuum lines I came across one that when removed from the connector under the air cleaner and plugged the engine idle smoothes out and there is a slight increase in rpm.

 

1st photo-inlet port in the air filter housing.

 

2nd photo-vacuum line from air filter housing connector to a fixed, vertical connector attached to the bracket where the back corner of the air filter housing is bolted.

 

3rd photo-tee off the lower end of the fixed vertical connector in 2nd photo and set back from the back side of the intake manifold. Vacuum line from the connector on the underside of the air filter housing comes in from the top left corner of the photo and connects to the top side of the fixed vertical connector.

 

4th photo-vacuum line from the run side of the tee ends at the manifold.

 

5th photo-vacuum line from the branch side of the tee rises upward, loops through a hose holder on the air filter housing and then goes to the windshield washer.

 

What is this inlet port in the air filter housing for and can it be plugged without causing problems? If so, my vacuum leak problem is perhaps solved.

 

Thank you.