I just replaced my son's blown 3.1 engine in his Firebird with a used 3.1 engine. It is in and runs well but I have a vacumn line I can't figure out where it goes. On the back of the throttle body there are two vacumn lines. A larger diameter and a smaller diameter. The larger one goes to the MAP sensor on the passenger firewall I believe. The smaller one goes into a tee and one side goes to (I can't think of what you call this) the connection under the upper plenum. My qustion is where does the other side of that tee go? I can't see anything disconnected so I am at a loss where it goes. Any ideas? Thanks, Bob

I think your refering to the fuel pressure regulator under the plenum and the other goes down to the divertor valve at the back of the air pump?.The ones at the back of the plenum..single port runs to the MAP and the other smaller one on the tee(with brake booster) runs into the ac/heater controls and tees to the "Orb of Power" (large plastic ball usually underneath the left front fender?.I think thats the route can correct me if I am wrong dont have diagram in front of me. So shot that one right from the head..

Thanks for the reply. I have passed it on to my son (I am on the road this week) and if he still can't find it, I will take another look this weekend now that I have some idea of where to look.

Thanks again!

Bob

Well, I had my son go crawl under the car and he traced the line from the orb back to the tee. From there he tells me it goes into the cruise control and the other end goes to the firewall, so I guess the one I am trying to determine where it goes does not go here. Any other ideas please?

Thanks,

Bob

Well, if I'm thinking of the right thing, and based off of the vacuum system in my '91 3.1 camaro...the larger vacuum line should run to the charcoal canister...the smaller one tees off and one end goes to the fuel pressure regulator while the other goes to the air management valve on the back of the air(smog) pump.

As for the MAP sensor, in the back of the upper intake manifold, there's a tee that comes out...one side runs to the brake booster....the other should go out a little bit and then tee off again....the tee should then go to MAP sensor....the other end continues to go on until it finally tees off to the cruise servo and the vacuum reservoir (orb of power).

Hope that helps...

Edit: I'll run out into the rain and check under the hood of my car real quick to make sure I'm right on that....

If you are right (and of course I have no reason to think you are not), then we are big time screwed up. I have a shop manual and it does not show vacumn lines. One thing it does say however is that the MAP sensor has a dedicated vacumn line and as the single larger diameter line from the back of the throttle body is just the right length and runs along the top of the engine to the firewall, I assumed that is where it went. The smaller line goes to a Tee, one side does go to the fuel pressure regulator (I figure it has to go there as the hose is just the right length.), but I have no idea where the other end goes. Do you know of anywhere that I can get my hands on a vacumn diagram? This is getting more and more confusing as I go along.

Please do NOT run out into the rain. But if it stops at some point I would really appreciate it if you could point me in the right direction, but I will gladly wait for better weather. Now I am totally confused.

Bob

Well, I went outside and checked and it's just as I described.

The vacuum systems for our cars are the same...I just doublechecked that, as well...

This is the diagram for ours cars...


And this is one that isn't....but I still found it helpful.


and you may find this useful, as well....

http://www.thirdgen.org/techboard/fa...-diagrams.html (Vacuum and wiring diagrams)

Extremely helpful. We have the lines all screwed up but now we have a chance of getting it right! Tahnk you very much.

Bob

I'm pretty sure that the line from your carbon canister to the throttle body has fuel vapor through out the line so if your gonna run the motor with the line loose you might wanna be alittle careful about it.

I'm not sure what I was smoking in my earlier post when I was talking about the line which goes to the MAP sensor....I just happened to re-read my post today, and realized what I had actually said...and just how painfully wrong it is.

So, I made this diagram today to make up for it...hopefully it'll help you and anyone else who is looking for one.

Feel free to distribute it.



If anyone sees something wrong with it, please tell me and I'll correct it. Thanks.

I have a vacuum nightmare that I have recently "inherited" when I bought an '88 2.8 to '90 3.1 conversion. This diagram helps a lot! Thanks for the extra effort!

Thanks for the effort this really saved quite a bit of time!