heinousacts

Hello all, I just bought my first 3rd gen camaro!
92 RS 305 TBI
It is kinda hard to start when its cold, and I noticed a "nipple"
on the back of the intake with nothing hooked up to it.
Does anyone have any idea what is supposed to hook up there?
Also noticed my heat only comes out the dash vents and there is a loose vac hose by the passenger firewall, but its no where near long enough
to reach to the intake and the diamater of it is to small even if it would reach.
Any help or pics would be greatly appriciated

camaronewbie

OK - your heat only comes out of the dash vents because that is the default setting when there is a vacuum leak, which you have since there's no vacuum line hooked up to that vacuum hose on pass side firewall.

You also have a vacuum leak on the engine itself, unless that nipple on the intake is plugged. So, you need to plug that at the least.

There should be, at the intake nipple, a check valve that has 3 inlets/outlets on it, one larger and the other 2 smaller. It should be installed so that the larger nipple gets connected to the intake nipple with a larger size vacuum line. The second nipple gets connected to a vacuum line that runs along the firewall to driver side fender, down the fender towards the front driver side headlight, and exits under the driver side headlight to the 'mystery orb' - ie the vacuum ball - this ball is a 'holding tank' for vacuum. The 3rd nipple of the check valve runs to that pass side vacuum line going into the firewall.

Here's the deal - engine runs, vacuum is sucked from intake through the check valve from the vacuum ball - the check valve keeps the ball 'full' of vacuum. The vacuum is run from the check ball to the heat/ac controls. The ball 'holds' vacuum for these controls - that way in a low vacuum condition (like at first second of WOT), you still have 'stored' vacuum to maintain the vent position of the heater controls.

Make sense? Hard to think about 'holding' a vacuum - intuitively you probably understand, hard to really pinpoint the tech of it though.

camaronewbie

Oh, there should be a vacuum diagram under the hood as well - might help you. If the sticker is missing - do a search on here for 'vacuum diagram' and see if you find one for the TBI motor - I know there's one here somewhere.

heinousacts

I plugged the intake vacuume nipple today and my idle smoothed out alot!
also during my search I found out that one of the plastic nipples on the egr solenoid was broke, so I replaced that as well. starting and idle are much better now.
I will get a T fitting tomorrow and hook it up to the intake and passanger side, and search for the one on the drivers side.
The sticker is no good, it only shows from the tbi to egr to the solenoid to map or maf dont remember wich one I have lol
Also dropped $25 on a chilton that only has the same pic as the sticker booooooooo!!
Thanks for the help I think I can figure it out from here.
Hopefully the lines to the mystery orb are still intact lol

heinousacts

First off thanks for the help camaronewbie!
I found the T fitting hanging below my master cylinder and hooked it up
Now I have some flow from whatever setting I have it on, but it still
comes through the dash vents at all times as well, and makes a hissing noise.
Im thinking I should replace all the vacuum lines under the hood, but
If anyone else has had this problem before I would love to hear about
how you fixed it before I go blowing a bunch of cash

camaronewbie

There may be a leak behind the heater controls as well - carefully pull them out and check the vacuum lines running to it - there's alot of colored lines from the switch that route vacuum to open/close different vents, and of course the main line in/out of the controller to the engine bay.

camaronewbie

Oh - your car should also have a heater diverter valve, pass side under hood, has 3 coolant hoses going in/out of it, and a vacuum line to the top coming from pass side firewall - make sure that vacuum line is in tact and connected.

What happens - vacuum line goes in to the cabin to the controller, where vacuum is routed through that switch with all the colored vacuum lines on it to open/close vents in the dash. Also, if you have the slider set to cool rather than warm, vacuum is sent out to the heater diverter valve to close off the hot coolant flow from the heater core so that no hot coolant is circulating inside the cabin (in the heater core) and adding heat when you want cool. Make sense?

heinousacts

Makes perfect sense, ill check the heater control valve first, I blew the hose on it that connects to the intake last week and had to change it out, maybe i left the vacuum hose off when i put it back together

heinousacts

Okay heater control valvue was all hooked up.
Switches from hot to cold just fine
I replaced all the lines from the Mystery orb to the intake
and im still not getting full flow outta where I set it.
The hiss is still there as well
It sounds to me like the flapper door is not closing all the way
and letting the air go through all vents and not just the selected ones.
I do get a change as I move it through the settings, so the door is moving, it just never blows out only the one I set it on.
Is the T fitting off the intake just a T or is there a check valvue in there that could be sticking?
Im thinking that I am just not getting enough vacuum to accuate it properly but I could be wrong.
Any sugestions?

camaronewbie

The T fitting is a check valve - maybe turn it the other way (maybe the check is facing wrong vacuum line).

Hissing usually indicates a leak behind the controls in the car - maybe that's the issue.