Exten Manifold Vacuum Question
 

1990 GXL N/A A/T

Had an engine fire so all my vacuum hoses got fried. Going through and replacing all of them and i've come to a bit of an issue. There are 4 vacuum connections at the bottom of the exten manifold where it bolts to the intake manifold. 2 go to the hard lines, 1 goes to the pressure sensor and i cannot figure out where the last one goes to. It is not labeled in the FSM. There are only 3 connections to the bottom of the exten and the only mention of it anywhere in the manual is pictured below. Something called the air breed, anyone know what this is?

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I posted the same question about a day before you did and got some replies, but nothing helpful. Maybe when guys start getting their cars out, someone will look at their intact car and give us an idea.

In the meantime, I sent my extension manifold to a shop to be cleaned and it came back with a cap on vacuum port on the front of the spark plug side of the manifold. The diagram shows this being hook into one of the solenoids. So I hooked that up and moved the cap to the mystery port that you and I can't figure out. The car starts and runs, but it's idling at 3K. I don't know if these are related phenomena yet.

Doug

Maybe it was capped. The early NA 2nd gen's had ERG valves (at least the 86 did) whereas the late 2nd gen's did not. If Mazda is using the same extension manifolds for all 2nd gen's, than there would be an unused port for late 2nd gen's.

BTW, have you made a determination of what caused your engine fire? This might be useful info for some of us as I also own a 90 GXL.

If I get a chance I'll look at my car tonight. All of mine are still hooked up.

I know for a fact that there isn't supposed to be a cap on the manifold at all.

The hard lines that hold the rat's nest on mine has an egr valve on it, of course it doesn't connect to anything, but it's there. it is completely hidden by the manifold though. I capped mine, but it can't be done unless you completely remove the manifold.

As far as the mystery valve goes, i wrapped mine from that cap to another portion of the manifold just under the rear of the throttle body. It was the only other unused valve in the car. Trust me, I checked. :D I'm pretty sure this is the correct set up but won't know for sure until either someone puts up pictures or I get my car started. I have another thread going under "Matthew Hamby" seeing what the possible causes are, and i believe it's the fuel injectors, going to get those flow tested and we'll see from there.

As far as what originally caused the fire, i'm really not sure. I was immediately thinking, failed pulsation dampener, but on the s5 it's welded, the only other reasonable thing it could've been was just a failing fuel line.

The previous owner had Mazda rebuild the engine 40k miles ago, and it was more than half-assed. They used the same old injectors, spark plugs, and i wouldn't put it past them to use some of the same hose and clamps.

After trying to start it up w/ some ether spray i got another fire that burned for about 5 seconds which i believe was caused by pressure at the primary fuel rails leaking from the injector seals. Not too sure on that either.

Once it's all said and fixed for sure, i'll be doing a write-up of these problems and a lot of other stuff i ran into recovering from the fire to save a lot of time and effort for people that go through this.

Somebody with an s5
 

Please go look at your car and tell us where this goes.

Being an S5 NA guy, we do not even have piping for an EGR valve in our rats nests. The 89+ do not come with one. Sorry to hear about you guys' fires. I have an 89 GXL and have seen all over the PD. It doesn't look like it can lsak but all it takes is a slight crack and a drip onto that hot exh mani. It happens frequently and not just to turbo cars so please don't rule out the rail/PD assembly just yet. Meanwhile I'll be here knocking on wood for my car to never go up. At least it can't burn down if it's parked in my driveway not running. :nod:

Native, can you run out to your car and tell us where that mystery port connects to or if it's capped?

Where does it come from? I can take some pics too if needed. Mine is completely assembled though, so hopefully I can find it and help you guys out.

Matt Hamby, can you repost those pictures? I'm on my phone and it doesn't want to cooperate with me.

Crap I was going to look at mine but forgot all about it.

Native, it's shown in the diagram in the first post. If you or RG could let us know where it goes, it would help the OP and me out immensely.

I can't see those in my phone though. Currently my only means of forum use. Sometimes I can see pics but sometimes not. I guess it depends on what you use to upload them.

not too sure how much this will help since its an s4T but it might give you an idea


[IMG]http://i44.photobucket.com/albums/f4...ps88f68b32.jpg[/IMG]

[IMG]http://i44.photobucket.com/albums/f4...psfb66b9e1.jpg[/IMG]


i too struggled with this until i found a pic and it was right.



i used the little pic in post number 4 and that helped a TON

https://www.rx7club.com/2nd-generati...rbo-ii-794890/

Sponge, your diagrams look good but we are working on the exact opposite of what you provided diagrams for. We are working on S5 NA, and the diagrams between even S4 and S5 are a good bit different.

On the extension manifold is a vacuum port that connect to the pressure sensor. There's an identical port to the rear of the manifold that we can't determine where it connects to. It makes the manifold symmetrical, but it doesn't show up on the diagram.

well that sucks. sorry dudes.

Thanks for the effort sponge.

Your two pictures answer your question. The 2 spots you've got pointed out in the top diagram are the two location at the secondary fuel injectors in the bottom picture. In the bottom picture the second from the right goes to the map sensor.

In the bottom picture, where does the one to the far left go?

On my car it is blocked off so I'm not sure what is supposed to go there.

Since we may have them hooked up incorrectly, perhaps it would be best if you would tell us where all four go.

Unfortunately when I remembered to look last night, it was already dark out and the car was outside. I'll need to take the plastic intake tube from the tb to the afm off to get a better look. I'm not sure if I'll get around to it today or not. If I can't do it today I probably won't have another chance until Friday.

I'm free today and can probably post a few.

Did anyone get any farther on this? I'm curious if I have something plumbed wrong.

Took another look ay this today. With it all assembled, the MAP hardline is obvious and the other two go under the secondary injectors, but the one under the rear of the BAC is capped on mine. I'm assuming it goes to the ACV or perhaps the air pump. Are these removed on your car?