I tested out an 87 T2 today and am thinking of buying it. The only problem I really noticed was that at idle the rpm drops when the brake is depressed. It also happens when the ac is turned on. I suspect its the BAC valve sticking or is just defective. My question now is: If the valve really is bad, can it cause a problem when smog testing? Also can having a bad BAC lead to major problems down the line? Thanks. Eli

 

Having a bad BAC won't really lead to problems, and it depends on your local inspections whether it will effect smog.

It is fairly easy to remove the BAC, clean it with carb cleaner, and reinstall it. If the problems remain, there is an issue somewhere else.

 

Oh crap. I cant believe you replied! I have your article saved to bookmarks. Very informative. Haha. Well thats somewhat of a relief. How can I remove the BAC?

 

Remove the two nuts and reroute the coolant hoses that enter/exit the BAC body. Slap a block-off plate over the hole and you're done.

But the even easier way is just to unplug the thing and leave it alone.

 

More importantly where is the Bac located?

 

passenger side of the intake i think

 

On a TII or S5 NA, the BAC is on the passenger side, on the upper intake, directly above the exhaust/turbo manifold.

On the S4 NA, it is on the dynamic chamber near the oil filler cap.

However I don't suggest you remove it. Removing the BAC means the ECU can no longer control the idle speed of the engine. The idle will then vary based on a number of things including load, temperature, phases of the moon, etc. Just pull the valve off, clean it out with carb cleaner and then reinstall. They almost never fail, they just get gummed up.

 

yeah if i'm not mistaken it is in charge of the cold start up phase where the car upon starting revs to 2800-4000 until it's warm then drops to 1500-2500 then down to 800-1100

 

The 1500 RPM idle is maintained by the cold start thermowax and cam assembly. The 3K startup is mostly the ASV.

 

Thanks for all the info guys. I didt go for it because after looking in the radiator I saw lots of bubbles and that just sounds like the engine will over heat on a long drive and thats what I need a car for at the moment.

 

Ha. The idle on this car was at about 500 or so.