The hose in question...
 

The bottom of the hose is close to and above the exhaust manifold. It gets very hot for long periods of time. This can be the result.

http://intertron.com/ron/images/aab2.jpg


The hose can soften and the leak opens when hot, but harden and still seal the leak when cold. When the hole is open, a vacuum leak results. The car runs poorly, maybe won't start, won't idle or idles at high rpms. Spraying carb cleaner or starting fluid in the area while the engine is running is difficult because of the position of the leak. Remove the hose and inspect it carefully.

If you find this problem on your car there are several ways to fix it. Electrical tape or radiator hose repair tape will work in an emergency.

Mazdatrix sells the factory replacement.

HOSE VAC 81-85 MANIFOLD TO ANTIBURN 13-7560-N201 $33.66
http://www.mazdatrix.com/c-5.htm

I'm sure some dealerships will get it for you also. Heater hose or fuel line and a brass connector can make a strong repair.

http://intertron.com/ron/images/aab1.jpg


5/8" IOD heater hose will fit over the nipple on the intake manifold while the one on the AAB valve needs 1/2" IOD. A little stretching or an adapter can make heater hose or fuel line work.

http://intertron.com/ron/images/aab3.jpg

12A Anti-Afterburn hose...no start, poor idle, rough running
 

This problem seems to come up often on 12A cars. Not sure about SA's, but I believe all FB's (with emissions) have this hose. It goes from the anti-afterburn #2 valve to the rear of the intake manifold.

http://intertron.com/ron/images/carb/c6.jpg

http://intertron.com/ron/images/aab4.jpg

http://intertron.com/ron/images/aab5.jpg

:) i replaced this hose whenever i installed my new intake manifold gasket, but just out of curiosity, do you know if they make any like..metal caps or something for that nipple on the intake manifold, (i don't have the rat's nest anymore) so basically i got a hose that goes from there topped off with a screw, i know they have vacuum caps, but i didn't wanna put a rubber cap and it'd burn off too lol, ...if not what's another alternative so that we don't have to change hoses every so often?

When I remove the nest, I use a large rubber Cap from the Parts store. Never had one melt.

when we had that at the dealership, we used to call it the mystery hose. its really hard to find in the parts fische

I stumbled on this post and it brings up a question I've had about a throttle connections. Can anybody help?

What is the correct position of this adjustable stop that sits on top of the linkage with the spring shown in the middle of this photo?:

http://intertron.com/ron/images/carb/c6.jpg

In the picture above it is shown mounted on the plate, but in the following picture the nut has been slipped up on to that spring loaded lever with the black plastic sleeve over the spring:

http://intertron.com/ron/images/aab4.jpg

Can anybody tell me which is correct?

Thanks
Ray

The lower photo is correct.

bStrange is correct - the bottom picture is where it's supposed to be.

And as for the original topic of the thread - I removed my anti-afterburn valve and sealed off the spot on the manifold with an appropriately sized bolt and some JBWeld. That's one spot which will never leak air again!

Jon

Thank you gentlemen! And I got off my ass and checked the FSM on that linkage hook up, they agree with you guys so the FSM must be right too!

Thanks
Ray

Here is how I blocked off one of mine.

Hose, clamp and...
https://www.rx7club.com/forum/attach...4&d=1175474359

a bolt. :)
https://www.rx7club.com/forum/attach...5&d=1175474359

The SA does not have the #2 valve.

Well since folks are showing off, here's how I did mine

https://www.rx7club.com/attachment.p...1&d=1225712556

That was on the manifold for Project Keiko:
https://www.rx7club.com/1st-generation-specific-1979-1985-18/project-keiko-part-viii-week-crazyness-796952/

The one that I have on my main car (Naomi) was done by Rx7Carl and it was blocked off with a bolt in a similar fashion, though I think he threaded the hole and put the bolt in that way, to make it removable. I've never tried removing it to find out.

Jon

I think this hose is one ive been trying to figure out on mine.

Found a hose that i think looks like this, in this general location, that the previous owner put a large bolt in. I pulled the bolt out and im pretty sure hot gasoline leaked out a bit. Is this normal?

Is this hose necessary? What does it do? the PO removed the rats nest.

The hose is part of the emissions system. The car will run without the hose and both nipples capped, but I would recommend doing it the proper way. Second from bottom link is emission removal directions.
http://www.mazspeed.com/faq3.htm

There are two other hoses in that area. One is about the same size. It is the vacuum supply for the brake booster. The other is a larger diameter removable nipple, fastened to the manifold by two bolts. It goes to the cat converter. These are often plugged with a bolt when the metal pipe rusts through at the cat and starts dragging on the ground.