Cruise Control Vacuum Routing

[waltsc13655]

I just purchased a 1986 Cabriolet and the dog gone cruise will not work. The car starts hard and the idle is high at one time, low another time. I believe I have vacuum issues, buit I cannot seem to find a complete set of diagrams that show everything like cruise control and A/C. Can anyone help or show pictures? The control valve only has one main vacuum line that comes out and goes to the servo but also has a "Y" that goes to the inside of the car. The vacuum control valve has 2 open tube connection and that is where I believe the problem is. Any help?

[CalAltaDubber]

Hi and welcome to TRF.

The vacuum lines are generally pretty simple on these cars. I can take som pictures of my '87 to help you, if you wish.

The main vacuum components are:

charcoal filter located in front of the front driver's side wheel, behind the fender;

Vacuum reservoir located just in front of the passenger door behind the fender; and

(for cars with AC) a vacuum reservoir located on the underside of the hood (often known as "the balls").

Really for the best information on your car you will need to purchase a Bently manual. They are a bit pricy, but far superior to all other manuals on the market.

Another great place for information is http://www.cabby-info.com. That is Kamz' site and she has lots of good information there.

Finally, post a picture of your car, we all would love to see it.

[kamzcab86]

Welcome to TRF!

Cruise control info, including diagram: http://www.cabby-info.com/engine.htm#Cruise

HVAC info: http://www.cabby-info.com/hvac.htm . Side note: In doing the site upgrade, somehow the link to the HVAC diagram was deleted, so I'll provide it to you here: http://cabby-info.com/images/HVAC/vacrouting.png (next site update, that link will return!).

[waltsc13655]

Thanks guys, this helps, but I still not seeing where the cruise control valve gets its vacuum from. If you look on the attached picture, it shows an open port. If this suppose to be open? This actually T's and had 2 open ports. Also, when I turn off the car, can hear a slight "hiss" from around the brake pedal. When I push in the pedal, it changes tone. It is certainly from vacuum, but not sure if it is from the brake booster, or from the vacuum switch. Is this normal?

[waltsc13655]

Sorry guys, can't figure out how to attach a picture...

[waltsc13655]

Lets try this...

[waltsc13655]

Picture of my 1986 Cabby

[gull]

To clarify what's going on in the diagram a bit:

- The cruise control system on these cars does not use engine vacuum. It has its own electric vacuum pump. It does not connect to the rest of the engine vacuum system.

- Vacuum goes from the pump to the actuator.

- The tee goes to a vacuum dump valve inside the car. Normally when you step on the brake or clutch, the cruise control is electrically switched off. The dump valves are a backup; if the electrical switch fails, the dump valve will vent the actuator vacuum to the atmosphere when the brake pedal is pressed, preventing the cruise control from fighting the brakes.