88 5kq Mystery vacuum hose

[S. Jaworski]

88 5kq

I got a big vacuum leak somewhere. Car runs fine, except it has rough idle.
Taking off the oil cap wont stall the engine.

I replaced most of the vacuum hoses and rubber doodads already. Did not
correct problem.

Today, I took everything apart again . . looking for leaking smaller hoses.

I found a mystery hose, which does not show up in the family album for this
year car. But it does show up for the 90 model year.

The hose(tube) has very small inside diameter and runs from a T connector
under the ISV valve that connects to a hose going to the fuel injector air
shroud. The third leg of the T goes to the air boot . .I think. The other
end of this tube goes to the back of the air filter box.

I took the air filter out . . but cannot see any openings for this tube . .
.maybe it connects thru internal filter container passages to the
differential pressure regulator?
I think the tube is providing a vacuum signal resulting from the shroud air
system. Something to do with for Limp Home mode?

The Bentley does not show the tube.

There is a pix of the hose in the family album:
A10Q, 1990, MG 1, S 33, Illustration 15-60        item 17

Any body know what the function for this tube is?

Syl
88 5kq
90 100q