I just took a look at my BAC, and there appers to be a hose missing from the top of the BAC. A hollow tube pointing straight up from the BAC, looks like it needs a hose! Does it really need a hose? Could this be why my idleing sucks? If so, how and where does it go! Sorry no digital camera yet, so no pics!!!

 

yes that's probably why it sucks. there is no pipe sticking up off the bac though (on a turbo...) but maybe you are thinking of the thing right above it? can't remember what it's called. it goes to the IC, which is off in this pic so my hose is too.

 

or is it NA, that one has one going up, you have to post more info when you ask questions

 

Sorry, I was in a hurry typing! It is a 1991 N/A.

 

ok, do you have that metal pipe next to it where that short hose goes?

 

NO, there is just a vertical pipe coming straight up. It looks like it is in the same position as the pic, But the pipe is straight!

 

Also, my BAC is on the passenger side... It says "BAC" on it, so I assume that is what it is I am lookin at!!

 

I don't know, the turbo one is one the pass side. but the NA one is on the driver side, I thnk you are looking at something else...

 

HMMMMMM... Well, it says "BAC" on it, it looks EXACTLY like the pics, and it looks like it is supposed to have 4 hoses on it! All lead me to assume it is the BAC. Mine is a 1991, could Mazda have put the BAC on the pass side in that year? Trust me, it says "BAC" and there is nothing that resembles it on the drivers side!

 

It says "N350" "BAC 12V"? But it is on the pass side! What does this mean?????

 

that pic was of an 88, so maybe, I have a turbo so I can't help you besides try and find pics on the net.

 

on 89+,the bac is on the passenger side.its sits on top of the upper manifold intake runners.i would be quite happy if somebody could post a pic of a 89+ setup also,as i am converting a 87 to the 89+ intake manifold,and i am having some problems relocating it because of clearance issue's,so it would be good to see how the 89+ setup differs.

 

Hey, Wankelhead, know about the missing hose? Where does it go?

 

well,i'm not really sure.see,the bac "system",as far as i know[from looking at a few scematics]is different between the different years,and,as i am keeping the 87 ecu,i will keep all my original sensors and "system" intakt the way it is.what that means,is,i just have to reroute/extend the hoses,2 cooling and the airhose. quite honestly[my project is on hold for a while]i cant tell you right now how the system works w/o taking another look at my scematics,its basic function in the 86-88 cars is to provide the engine with more air[to get a higher idle]to compensate heavy alternator loads,so it takes air pre-tb,and bybasses it when the valve is open.i'm not real sure what role the asv has in all this,but as you can see in the pic,they are all connected.so,either look up some egr/vacum scematics,or,ask someone with the 89+setup.correct me if i'm wrong,here,guys.
sorry i could not be of better help...

 

Yes, it needs a hose. This hose is the metered air supplied from the Inlet Duct somewhere close to where it is attached to the throttle body. Not having the hose connected to the BAC will definitely cause a bad idle, because you are sucking air into the BAC that has not gone through the AFM (Not to mention it is bad to suck unfiltered air into the engine), and the hole/hose that is disconnected is also a source of unmetered air into the engine. I can't give you the exact location of the hose on the Inlet Duct because I don't have an 89+ NA car, I can only tell you what that pipe is for. Good luck finding the hose/hole on the Inlet Duct.

Irv, Keith's dad

 

And 'yes' the BAC is on the passanger side of the engine, but I don't recall a hose sticking straight up. there is one or two hoses coming out of the bottom though.

I'll take a look and see where they go...

 

My compliments on Scott's good pictures.