I figured out why my FD doesn't pass emissions and its because the ACV always dumps air back to the air cleaner. I haven't taken the ACV out to look at, but I suspect a old hard rubber diaphragm thats cracked.

Anyway, looking at the Mazda service manual diagrams leads me to believe I might just be able to plug the air pump air relief hose to force the air through. Admittably, I don't understand the why there are 2 solenoids for air relief (does anybody understand the distinct roles relief1/relief2 play?) but it looks like theres always a open path through the split air bypass so it doesn't seem possible for the air to have nowhere to go (which would probably be bad for the air pump).

Has anybody tried something like this?

 

I'd just get a good used ACV and swap it in. The ACV is pretty easy to get to - pull the upper intake manifold and there ya go. I'd also make sure the vacuum lines going to it are hooked up properly.

Most of what and why the ACV does things is something of a mystery.

But, I have also heard that a quick and dirty way to get by emissions is just to put all the airpump's output to the main cat. That gets it nice and hot, which is what's needed for the cat to really work and pass emissions.

I will have to say that I have not ever had to worry about emissions and I'm passing on what I've heard and read. Do some searching and see what you can come up with. Good thing is many people have been in the same boat you are.

Dale

 

You can buy the diaphragm

 

The diaphragm is actually a check valve.

You can purchase a replacement from Ray or your local dealer

1480-13-730 VALVE,CHECK $12-$15

 

Getting to that ACV was a P.I.T.A. I really probably needed to remove the solenoid rack to get the third "hidden" bolt on the ACV, but was afraid of not putting it back in right so wasted a lot of time.

It looks like the check valve for port air (pinwheel looking thing) is okay.

What looks suspicious is the big spring-loaded vacuum actuated plunger that opens the path from the air pump to the dump hose. Unlike the other spring loaded valve, the plastic plunger tip piece is rattling and not attached to the solenoid.

Gonna get a used one from Glen at Arizona Rotary Rockets (great shop BTW) tomorrow.

Heres the pics of the broken (?) ACV and the good check valve.