Need help identifying Vacuum hoses '90 2.3L LX Convertible


New Member
Sep 7, 2010
Phoenix, Az

I would like some help identifying some of the hoses coming out of this vacuum distribution manifold, located on the drivers-side firewall. I cant find a picture of this in my Chiltons manual.

This is on my 1990 mustang LX convertible, 2.3L 4-cylinder, automatic transmission, air conditioning

1. Goes to Air filter

2. ? (transmission possibly?) runs rough when unplugged

3. ? Thin vacuum line going to some diaphram on the firewall, located at the top of passengers side firewall. It looks looks like it opens/closes a vacuum circuit possibly for the air conditioning.

4. ? This hose looks like it goes into a computer module (BAP or MAP sensor possibly) mounted on the firewall, a few inches to the left of this vacuum distribution manifold.

5. Goes to the charcoal canister.

6. Goes to brake booster assembly.

7. ? This vacuum line just dissapears into the drivers side fender/firewall (about where the two meet).

8. This is capped (looks factory)

9. Goes to the upper intake manifold. This I suspicion is the main source for vacuum going to this distribution manifold.

Any help is greatly appreciated

Thanks, Steve


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Oct 7, 2010
I checked my car

I have a 92 but most of these should be very similar. I will head outside and take a look.


[walks outside]

[opens hood]


OK this is what I found. Compare this to your own vehicle:

1. Is attached to a red plastic line to the EGR EVR solenoid that controls the EGR valve.

2. Was attached to my vacuum modulator when I had my automatic installed. If you pull this one, you will create a continuous vacuum leak and the car wont shift correctly. On my car its now capped off because I converted her to a 5-speed.

3. Is attached to a black plastic line to the Air Cleaner Bimetallic Switch in the air cleaner housing. This controls the warm air that enters the air cleaner from the engine stove when the car is cold.

4. My car does not use this.

5. My car does not use this.

6. Goes to the brake booster.

7. Proceeds to a black/white check valve and then out into the driver's-side fender and to the cruise control unit. You will note the throttle cable to the cruise control also descends to this area.

8. My car does not use this.

9. This is the most important hose it goes to the intake manifold and powers all your vacuum-actuated systems.

Any more questions? :nice: