DivinDriver

iTrader: (15)

Well, the ACV on the FB is a little different, but the concepts are similar.

There's a large sprung valve that goes right thru the middle of the ACV, one side of it is on the air feed from the air pump & goes to the air injection system & the cat feed eventually, and the other leads to the bypass line that goes back to the air cleaner. This valve is opened by pressure on the pump side, which in part is governed by the condition of the diaphragm-controlled valves on the rear part of the ACV.

This valve consists of a round metal disk, with a rubber lip around it. There's a hole in the center of the disk, with a bushing around it (makes the disk thicker in that area). The disk slides along a shaft, and pushes against a spring.

The spring holds the disk tight against it's seat, but air pressure from the pump can push it open, letting air bypass.

When brand new, the hole in the disk is only slightly larger than the shaft it slides on, and it's coated with a fairly thick grease. So, not much air can leack thru unless there's enough pressure to push the valve open.

But, as the ACV ages and that little disk has slid back and forth on the shaft a few million times, the hole starts to get bigger. And the grease ends up going... somewhere.

Air starts to leak thru the hole, which reduces the pressure available for the air injection system, and also the split air that goes to the cat. It also means the bypass doesn't open as early either, because it's leaking. Worn badly enough, the disk can even "wander" around on the shaft, and not seal properly at the edges when closed.

The other parts of the ACV can also fail; the diaphragms for the vacuum-controlled valves, and the springs that work them. Mechanical stuff, can all wear out. But I've noticed this wear pattern on two AVC's that were otherwise fine.

Here's a couple kinda blurry pix I took, back when I got my last new valve.

View of the disk and shaft, from the manifold side of the valve:


This valve is fairly new; notice that the shaft fits pretty tight in the hole... though there's no grease left:


This valve is very worn; note the hole is huge.


Now, I don't have absolute proof that this is the only thing that causes ACVs to fail, but based on what they do, that degree of wear is going to let a lot of air that's supposed to go to the AI or cat instead flow out the bypass, screwing up the pressure balance of both systems.

my1st7

Thanks, an excellent post. I will start with the ACV , hopefully Friday. Will let you know how goes.

j9fd3s

iTrader: (3)

http://www.jimrothe.com/mazda/84_tra...ual/index.html

section 4a has a good explaination of HOW the emissions system works. basically on the catylist cars when the air pump air is going into the exhaust ports you pass smog.

the thermal reactor cars are different

kashe

It is hard to find a new acv but, I called the referee and they gave me a number for a shop that re manufacturers them for 165.00,
Discount Smog 1-866-965-0912

I hope that will help

DivinDriver

iTrader: (15)

Understatement of the year, there. 'Different.'

j9fd3s

iTrader: (3)

haha, yep! i dunno how it works (except in concept) because ive never had to fix one

my1st7

Since my car won't idle after warmup " choke" I checked my ACV during warm-up. Dont know if that makes a difference. Air was blowing out the hose to the air cleaner so hard you couldn't hardly keep your head over it. That's when I noticed my cable was not hooked up to the "teeter totter". I turned car off and hooked it up. When I checked again there was NO air coming out the hose. Therefore, I presume my blower is working and my ACV is working. But, because my ACV WAS not working it probably ruined my CAT. If my CAT is clogged can you unclog it or just buy a new one.. flame away on that one.

kashe

I got my car to pass smog !! The carb was rebuilt old acv new cat, i also removed the altitude compensator that is all it takes! good for two more, hope the smog laws change

DivinDriver

iTrader: (15)

Grats!