i have been working on my car and im learning new things and i just need to know what a BAC valve is so if there is any one who can let me know what and where it is on my car that would be awsome. my car is a 1987 none turbo 13b

 

try searching the FAQ or just the 2nd gen section in general, its in there

 

Go here FAQ-FSM

 

Device that varies the amount of bypassed air according to engine load to keep the engine from stalling when p/s, a/c, etc. is turned on. Idle should raise about 100 RPM and I believe it only functions at idle.

I've an S5 Turbo, so it's probably different, but the FSM knows for sure.