I have a convertible...and I tried my air conditioning at some point and no air flow from upper air ducts...no ac at all...didn't really care since it's a conv.

Having other problems I have been reading shbox site for everything...I found the vacuum check valve paragraph... the picture doesn't really show the part which is broken, the dashboard mode selector. It's been broke so long that you can't even tell it's broke..the plastic all looks the same.
http://shbox.com/1/vac_check_valve.jpg

I looked it up on autozone.com and found part #47150 which makes it OBVIOUS that mine is broken... What does this thing do...just allow your dash air to work properly? Or does it have some other purpose as well?

 

The engine pulls a vacuum under most conditions, but not all. So the HVAC vacuum system has a small plastic reservoir in the passenger front fender to "store" vacuum. The check valve prevents the reservoir from losing vacuum when engine vacuum is low (e.g. at WOT). Without the check valve, when you put the pedal on the floor, the flapper doors would return to their "no vacuum" position. With the car idling or at low load, the check valve isn't really critical. If the flapper doors still won't work under those conditions, most likely you have a leak somewhere in the system.

 

Okay I bought the new Vacuum Check Valve for $4.23 it's a universal which looks exactly the same as the old one so I got it. Here is a pic of the old and new one. The broken piece was still in the line going to the "mode selector" on the dashboard.


Here is a picture of the old one and the broken piece which is on the end of a Drywall Screw...I screwed the drywall screw in about 5 rotations in order to pull the broken piece out of the vacuum line going to the dash.


I am thinking the Valve is a 2-way valve for which only one-way was broken (dashboard mode selector-way) and the rest of the system I'm assuming is O.K.

I don't really understand what your saying...the flapper doors are for the air flow inside only? or for engine performance? This is what I was trying to ask. I have been having engine hesitation/surge/stalling(one stall) and am trying to eliminate this as a related problem

I finished installing the new check valve and once I started the car and turned on the interior dash vents they WORKED GREAT...blowing hot and cold air like a CHAMP!

If the bottom part of the valve was broke (Intake Manifold) what would happen? same interior dash no air problem or something else?

P.S. If Rob wants to use any of my images on his SHBox.com site feel free to do what you want with them. My way of paying back for the help it's given me as well as maybe make it clearer for others.

 

If part of the check valve was broken off, you had exactly what I said you had - a vacuum leak. The "flapper" doors are the doors that move in the HVAC ductwork to divert the air flow to the vents, the floor or a combination of both. They have nothing to do with engine performance. A vacuum leak would also cause the engine to run poorly. If any connection on the vacuum valve breaks off, you have a vacuum leak.

Look at the diagram (also from Shoebox's site). Your vacuum check valve internals were probably fine. What broke off was the line from the check valve to the control panel. The vacuum actuators for the flapper doors are labeled 32 - 35 in the diagram, and the dashed lines show the flapper doors each one operates.

http://shbox.com/1/hvac_vacuum.gif

 

OK I understand that there was a leak and in my case the leak being a broke connection on the vacuum check valve was a really easy and simple fix. I understand that this works with the HVAC system and is what didn't allow my dash vent "flapper doors" to open leaving me with only floor air.

But here is where you confuse me...
"They have nothing to do with engine performance. A vacuum leak would also cause the engine to run poorly."

Okay so which is it? The leak that I had can or can't cause my engine to run poor?

 

Why are you having so much difficulty with this?

I said in my post:
A vacuum leak affects the engine, and can make it run poorly. What part of this do you have a problem with?

If you want to nit-pick some more... a vacuum leak "can" make it run poorly.... but does not ALWAYS cause the engine to run poorly. If its in a location where the PCM can compensate by adjusting the long term fuel corrections, the only affect it would have might be too high an idle.... but then again, if the vacuum leak is small, the PCM may be able to compensate using the IAC valve counts.

And to further clarify.....

The flapper doors control the HVAC air flow, and have NOTHING to do with engine performance. The fact that the vacuum leak happened to affect the operation of the flapper doors does not logically lead to the conclusion that the flapper doors therefore affect engine performance.

At this point, I'm actually sorry I tried to help I'll know better this time.

 

Okay, SORRY, I reread your post again after some sleep and now I get it...it was clear the first time if I read it right. Not your problem mine...but PLEASE don't hesitate to HELP just because of this. I drove the car and watched the TACH as I accelerated hard and after all the other work (spark plugs, wires, cleaned and reseated opti-wire harness with broken clip, cleaned MAF and k&n air kit, oil, radiator fluid, t-stat, master cylinder, fuel injector cleaner, vacuum check valve) my RPM's stayed pretty smooth and didn't go near the red at all.

Once again sorry I misread your words... but your definately helping me a lot!so please don't stop!