We were testing the BAC and using a 9v battery to activate the solenoid. The solenoid works fine but it seems like the valve doesnt completely close. We have a hose and are blowing into the port. There is a rubber gasket or diaphram that is torn.

Should the valve seal completely?

 

Turn the screw all the way in and see if it seals then.

 

The idle screw is screwed in all the way.

 

The little pipe on the side? That pipe doesn't seal against the body of the BAC very well. There's a set screw on it so you can remove it, and it just sticks in the BAC body, no seal there. If you can blow from the other end and it still doesn't seal, try cleaning it with some throttle body/intake cleaner. Might just be gummed up.

 

I thought you meant the idle screw.

I had it off to clean it with carb cleaner. After flooding it with carb cleaner i decided to test it to see if it sealed.

I saw that you can burn out the solenoid if you leave power on it too long. Any idea what too long is? I was surprised that it was open by default instead of closed.

 

I was talking about the idle screw at first, but then I realized you said you were blowing through the little pipe on the side. They can be burned out if you apply voltage to it too long. How long? No idea. It's a pulse width modulated solenoid, meaning the ECU pulses 12vdc to it, and it varies the amount of open vs. closed time to allow more or less air to bypass the throttle body. It is normally shut too. Not open. If you unplug it, it shuts and the engine will die or struggle.

 

The idle adjustment screw is closed tight and has been. We are blowing into the 5/8" feed elbow that comes from the hot/power pipe that connects to the turbo outlet. So it appears it isn't closing because if I understand correctly with no power to it we should be able to blow into that feed elbow and no air should come from the square opening the feeds into the UIM. Some may leak from where the elbow inserts into the BAC.

I'll test again. Thx

 

At worst, that will give you a slightly high idle. Does it leak a whole lot, or is it just a little? If it's just a little pressure eekin' by, it's really not that big of a deal.

What's the problem you're hunting down anyways?

 

Bac is a really cheap part if you need to get a used replacement, all it does is bring up the idle when there is electrical load bringing the idle down (heat/ac etc), so thats why if it's got a leak it will bring the idle up more than it should

 

BAC opens/shuts at about 120hz and goes open all the way at START positon of the key and stays open til the key is put to ON/RUN then goes and does it's duty cycle as dictated by the ECU.

ECU determines the duty cycle and if the ECU's BAC transistor is shot.........it has no duty cycle at all and most likely won't open when the key is put to START.

Remove the BAC and leave its electrical plug on it. Turn and HOLD the key to START. The BAC should go full open (which isn't very far at all) and stay open as long as the key is to START. IF it does not do that...........transistor in ECU is shot OR elect terminals in its plug might be pushed back not making contact with the pins in the BAC.

 

It leaked a lot thru the torn seal so we modded an N350 BAC and put it on. Works marvelously.