Guys since no one seems to know what the Hell I'm talking about with my fire-breathing ACV, I took it upon myself to come up with a plausible cause.

Background:
The ACV was shifting extremely hot air into the airbox, to the point where it started melting.

Well I got to thinking. The ACV is supplied by the airpump, right? No way the airpump is going to get that hot.

Next, it goes either to the cats or back to the beginning of the intake. Since this is pretty much a closed system, I have come to the conclusion that the hot air is coming from the exhaust.

But the ACV doesn't flow that way, does it? That would be backwards, right?

Well WHAT IF my cats are so clogged that the exhaust has nowhere to go but straight back up the feed line on the middle cat, into the ACV, at which point it overpowers that pathetic little spring in there, cooking the plunger to the point of inoperation, and proceeds on out the top, where it scorches everything it comes into contact with?

My proof so far is a glowing red exhaust manifold, along with my suspicion for quite some time that the cats are shot. Yes I said that exhaust manifold is glowing red; underneath the heat shields I saw tonight.

Anyone feel free to refute my evidence or introduce another theory I have very little to go besides my best hunch, and as always I'm open to suggestions

 

huh, sounds like a pretty sound possibility to me.

 

glowing cats? Your theory sounds very plausible. Disconnect them and test.

 

only one way to find out...punch them bastards out and take her for a spin!

 

Actually I checked the cats and I could not see them glowing. But when I looked under the hood, yes, that big block of iron was red hot.

 

is power down? thats a symptom of clogged cats.

 

Could be running rich too, that would cause the header to glow red (ask me how I know). Also, when my trailing coil wasnt working (disconnected wire), the header started glowing too.

~T.J.

 

If it's too rich, then it should run cooler shouldn't it? Unless I'm just thinking of aircraft type engines....

 

I just polished all the connections on the ignitors and tested them 2 weeks ago. I'm pretty sure they are working.

I also set the mixture to 3 1/2 turns out and adjusted the idle mixture screw to ~900 rpm.

I don't know about aircraft engines, (are you thinking of the radial type rotary engine?) but too rich on a rotary will cause it to run on the hot side.

 

Rich is cool, Lean is hot, for any internal cumbustion engine.

@Suparslic, if your cats are not cloged it is very possible that you are burning water. Does your radiator always seem to need filling?

Ryan

 

I have a theory as well: Block off the ACV with a blockoff plate and test.

 

When my cats collapsed, it caused MAJOR power loss, almost to the point where I couldn't start it because no air could move through them. It doesn't sound like that.

 

There's a 1 way check valve in what Mazda calls the "split air pipe" (i think, crazy names) that supplies air to the main cat. This should prevent any exhaust entering the ACV/airpump, HOWEVER if your cats are shot then it's possible it ate the check valve. The checkvalve is a fat section right after the upwards bend of the metal pipe that runs from the main cat into the engine bay. It's not hard to see, since right after the check valve it turns into a flexible rubber hose that goes to the ACV. You'ld think the hose would melt long before it blew exhaust into the system. Is it possible that the ACV itself has malfunctioned? I thought it's job was to blow some fresh air from the airpump into the exhaust mixture that got mixed in with the next intake charge. If the ACV is malfunctioning I suppose it could be reversing the flow and blowing back through the system, tho the airpump should supply about 2-3psi of air into the system so it seems unlikely that it'd reverse the flow without some damage to the airpump itself. I might be way off here, but I'd check your airpump, if it's not working right there's a cause for your cats to glow hot, which might have caused other things to go wrong.

So, in short (I seem to like to write bibles ) check the airpump, is it indeed putting out cool, fresh air? then check the check valve on the split air pipe (should only flow towards the cat) then check the ACV itself.

good luck
matt

 

Cooler engine, perhaps, but your EGT's will go up because of the mixture burning in the exhaust manifold. (unburnt fuel hits oxygen and hot metal, hence the famous rotary backfire )

That can indeed cause glowing manifolds. Trailing plugs not firing = not completely burned mixture exiting the exhaust ports, where it burns more

--matt

 

There are check valves on the air tubes to the cats, If one were to fail, the backpressure would cause the exhaust to travel through the ACV backwards, and I suppose into the airbox. Now, how, or why these check valves might fail, could possibly be linked to a failing cat, I suppose.

 

I just pulled all the hoses, revved the engine from the carb, and no its not a failed check valve in the air line thanks Speckamp. Also the other hose to the airbox blew air that got pretty hot after a few seconds; and I can tell where its cooking the engine bay in the new direction I pointed it.

So much for my theory

Basically the extremely hot air coming up from the ACV has nothing to with exhaust heat, as far as I can tell. I'm going back outside to see if I can test the airpump, I guess remove that large hose that goes to the intake? Damn that thing is a PITA...oh well I'll be back as soon as i find something out.

Thanks everyone I'll post later...

 

Well the airpump seems to be working fine. I did notice an awfully stong gas smell while I leaning over the engine; i think it was blowing out of the port on the exhaust manifold cover.

Sooo what next I guess I will remove the ACV cover hopefully I can pull it off w/o pulling the carb

 

Well that was awesome. I was missing a plunger in the ACV assembly;actually the one on the manifold side. I must have forgotten to put it back in when I had this thing apart last summer.

Lets hope that was it and not that it burnt up.

Well the car is back to her old self, I luckily had a spare intake and ACV.

The only problem is that threads on the intake are stripped; I can't tighten it down and I have a pretty serious vacuum leak now...

but I can swap my other intake on later, it still has good threads. I am so happy right now because my car hasn't been running right for weeks.