I have searched and found many threads. However, none with any pertinent advice especially considering the circumstance I have. As the title suggests. I am aiming to reinstall my BAC that was removed along with nearly all of the emissions on the car by the previous owner. I have most, if not all the parts as far as I am aware that were taken off.


Problem: I do not know what rubber hose attaches to the end of the BAC due to emissions delete and catch can install.

Pictures as follows:

Catch can installed by previous owner. Hose is connected from nipple in housing into catch can. Second line runs off catch can and connects to a hardline on the firewall.




Hose off of housing




This is the hardline that it is connected to.





Block off plate



Am I missing hoses that would connect to both ends of the BAC? I appreciate any help as my cold start issues is very irritating.

 

There are three hoses in all which connect to the BAC. Of these three hoses, two are coolant hoses, which are not really relevant to the operation of the valve. The intake tube coming from the AFM has an elbow underneath it before it reaches the throttlebody. This rubber hose from the elbow connects to a metal tube behind the throttlebody and travels from the passenger side of the throttlebody to the driver side of the throttlebody. From there a hose connects the hardline hose to a rubber hose which feeds the BAC.

 

Thanks for the response. I should have mentioned that this car has the rats nest removed as well. That being said, I can't locate that hose you mention. There are a lot of nipples capped off and I am starting to wonder if that entire hose was removed. I apologize if I am asking a bit much, but could you post a picture of that hose?

I really appreciate the help.

 

There is a hose that runs "behind" the intake. I believe it may even be metal in the middle. However, based on your pictures, you don't have it. Not to worry. Find some hose at the auto parts store that will fit on the BAC valve inlet. Then run that hose to the main intake, there should be a little black elbow/tube sticking out. That's where the BAC valve gets it's air feed from.

 

Here's a pic showing an engine bay for a non-turbo s4. It's not completely stock, but it clearly shows the location of BAC and it's related parts. Thanks to need RX7 for originally posting his engine bay. Also, that catch can mounting seems like a waste. You won't be able to utilize most of the can and the sight tube serves no purpose. I'd look into relocating in so that it was vertical instead of horizontal liek in the second picture

 

Thanks for the pictures and input. It seems that plastic elbow that connects off the intake has been removed as well. Anyone got a spare I could take off their hands?

As for the catch can, I wanted to remove the whole damn thing. As 3vil stated, it is mounted horribly and it isn't even baffled. Debating just capping those lines off as well if it won't affect vacuum. Maybe I will turn it into my coolant overflow bottle. Meh.

 

Check the 2nd gen parts for sale section.

 

Sorry to revive my old thread. I have accumulated all the parts to reinstall the BAC and have done so recently. However, after installing I now get a 12-1500 rpm idle surge. I have checked for all vacuum leaks, all connections are installed and/or capped off if unnecessary. Could this be a sign of a faulty BAC? Holding down the accelerator until the car warms up is getting old.

FYI, When removed I have no idle surge but the car still dies unless warmed up (original reason for reinstalling BAC).

 

Did u remove the catch can set up. It looks like that was setup for the crankcase ventilation. And you probably just need to readjust ur idle/tps. I've been going thru similar problems with the cold start. I believe its the thermowax not working right in combination with a faulty BAC. Do you have the rear iron coolant hose attached?

 

TPS and idle has been adjusted several times and checked. Still holds true readings. Coolant line to BAC valve is non existent. From what I understand, the coolant hose that connects to the BAC is unnecessary and is only meant to stop the valve from freezing up.

As previously stated, when I remove all the BAC components it runs fine minus cold idle (which will happen with the BAC removed)

 

The 2 coolant hoses to BAC don't matter but the rear iron one goes to thermowax I'm pretty sure. If the other 2 were not hooked up the rear iron one probably isn't either which u would need for the cold start issue. Idk if u could just use the rear iron hose and block off the other 2.

 

If the fast idle system is intact but is not receiving coolant, the throttle valve will stay open and you will have a high idle.

 

Problem solved. Turns out one of the vacuum caps had a tiny hole in it. Car now cold starts and holds idle fine unless its below 10 degrees, then it takes a couple minutes and then holds idle fine.