Hello Members!
My BAC (idle air control) valve diaphragm on my 1985 GS has deteriorated and has prevented the car from passing smog. The mechanic states the valve isn't triggering the oxygen sensor so the catalytic converters can do their job. Is there a service that can rebuild these things or better yet, a new one. Thank you in advance for your guidance!

 

Sounds incorrect to me. BAC only maintains the idle. Plus 12A does not even have one.

Sounds to me like he means ACV. It controls air flow from the air pump to the cat. If you must pass emissions I suggest routing the air pump straight to the split air pipe.

 

Thank you for the recommendation, I just may have to resort to that modification though I'd prefer to keep everything original. I took apart the acv (thought idle air control valve was the same thing) and found one of the diaphragms toast due to the proximity of the exhaust, the other was still flexible and in good shape. Perhaps a material with higher heat resistance like silicone would be the answer?

 

for the test, you can shim the ACV to flow to port air, and it'll pass the test. you don't want to leave it like that though, it is hard on the cat.

 

You can purchase a new diaphragm through Mazdatrix I think. Although, I have connected a hose from the back of the air pump straight to the split air pipe and passed. Being your in CA they presumably do visual checks and may notice a non factory hose. So the shim idea may be better. You could just carve out the inside of the gasket.

 

Thank you for the info, I'll check into it!