Vacuum questions

[odjeep]

I have an '87 wrangler with the 258 and I was wondering about the vacuum switches located above the valve cover on the fire wall. There are two side by side with a wiring harness coming from them. Are they emissions related or somethin else. They are currently unhooked but I was wondering what they were for. Also, how is the vacuum hooked into the heater controls. I've noticed the vacuum hook-ups on the back of the controls but have no idea what to hook to them. Any help would be appreciated.

od

 

[Bounty__Hunter]

One is for the 4wd light on the dash and should get source vacuum from the front axle disconnect or the transfer case, I'm not sure.

Don't know what the other one is.

 

[odjeep]

The 4x vacuum switch is hooked up and works fine, its further towards the battery. Thanks anyway Bounty.

 

[XJNick]

fixin my defroster and heater

This is just a guess, since I'm not certain on the placement of stuff for the 258 I6, but they could be:

> Manifold Absolute Pressure Sensor (MAP)
> EGR solenoid

As both of these switches are vacuum-electric
-Nick :!:

 

[skyjeeper]

no map- carborated
4.2's and early 4 bangers used a transducer, 4.o's and later 4's used the solenoid.

i want to say they are for the p/air check valves for the pulse air system, but i'm not completly shure. i removed them a long time ago with the rest of the emissions controll stuff. sorry, those are two of three mounted on a bracket ON the valve cover. i'll have to take a look if i make it outside later today. i'll let you know.

 

[XJNick]

no map- carborated

Good Point :mrgreen:
-Nick :!:

 

[odjeep]

I've taken the group off of the valve cover and the pair off of the fire wall. I guess since they've been unhooked this long and haven't made a difference I don't really need them seeing as how the emissions system is..well lets say its not to factory spec :wink: . Thanks anyway guys. Any thoughts on the heater controls. Should I just supply vacuum to it and see what happens or what. Thanks.

od

 

[richsia]

They're stepper valves for your Pulse Air System. If you're pulse air's not functioning, then you can remove or block them off.
They're useless if you're not running with stock emissions

 

[skyjeeper]

i don't know of any vacuume lines to the heater controlls.

are you talking about the stepper valves like richsia is talking about?

if the point to hook up the vacuume lines to are in the engine compartment just forward of the battery, those would be the stepper valves. they each have a spot on top to connect 5/8" (or so) vac line to go to the underside of the stock air cleaner, and a point on the side for 1/4" (or so) vac line to the vac switches on the valve cover (correct me if i'm wrong). they have a hard line on the bottom. one goes to the cat, the other to the exhaust manifold, or just below it.

if you still have the stock cat and remove theese, you will have to plug the holes. (i'm going to set it up so that i can pump air into the cat so i can still pass inspection. shh..don't tell)