AIV Valve

[kwilley]

I was wondering if anybody knows why that AIV box is so important and so hard to find replacements for? I have an '87 XE-V6 and a couple of years ago, I noticed a little rust on that round box under the air intake (which I finally found a 2 paragraph section in the Chilton manual is an AIV Valve). Within 3 months, it was completely gone as was the metal underneath. There was suddenly a large hole from the engine compartment into the driver's side wheel well where I could see the tire. The engine started getting really sluggish and began stalling. I took a good look at everything and realized that my ENTIRE exhaust system was destroyed.

 

I have been replacing parts as I can (have a different daily driver) and have seriously had to purchase every part from headers to the tail pipe. I do not know if it was the catalytic converter or the AIV that went first, but apparently one affects the other in a chicken or the egg situation. I have finally tracked down that little AIV thing at a Nissan dismantling yard in California, but it wasn't easy. There is absolutely NO MENTION of this part anywhere on the internet, nor can you find a replacement for it. I had a hard time finding anybody who even knew what the heck I was talking about. My dad has a friend who rebuilds and races and he told me that this part is a feedback loop, and that not having it will make the exhaust system die a quick and painful death (again).

 

Does anybody know what exactly might have failed in this situation so I can avoid it in the future?

 

Or exactly what the AIV is and why it can kill your Pathy?

 

Thanks!

[88pathoffroad]

The AIV is an air induction valve. It controls the amount of air fed to the catalytic converter or exhaust to help it burn unburned fuel more completely. There are check valves in the case that are supposed to prevent exhaust gas from being fed back through the case and into the intake. All it does is feed outside air to the exhaust when the exhaust pressure is negative.

 

It's totally dedicated to emissions, nothing else. I took mine out and haven't noticed any problems, my exhaust is still in decent shape after 5 years or so.

[kwilley]

Does the AIV hurt performance through emissions? When the engine is running, I definitely have exhaust gas going to the valve. That is, I am sure, where the hole in my engine bay came from. Did you just stop up the tubes running to and from the AIV? That is what I have done for now.

[89_trailboss]

when I cut my cat out I just cut the tube and left it. no power difference in either way.

[mws]

When functioning correctly, it will not hurt performance in any way. It just allows more air (oxygen) into the cat so it functions as efficiently as possible.

 

If not working or eliminated, the cat may not get enough oxygen to fully convert pollutants so it may or may not pass smog tests.

[kwilley]

I live in Tennessee and don't have emissions testing or anything. Although I do love anything that hinders the performance of my Pathy, I may just leave the AIV out completely. I just have all the tubes capped off now, though I have a new (to me) AIV sitting right here waiting to go in (maybe).

 

I am, however, still wondering why my entire exhaust system rusted out. My mechanic said he had never seen a complete system rust from the inside out like that.

[88pathoffroad]

Maybe they used crap piping originally. Wierd.

[mws]

Most usual cause of that is lots of short trips. Whenever an engine is running, it produces water vapor. If the engine is operated for quite a while, all the exhaust components get hot enough to evaporate most of the water. But if run for only a few minutes, the exhaust tubing and components are not hot and the water vapor condenses on the steel. Repeat that cycle a few thousand times and you have quite the rust generator...