# 92 Nissan D21 4cyl- WATER in the AIV filter!?



## L olver (Feb 4, 2008)

Here's a good one for ya folks!
I've been experiencing a weak starting condition and stalling at idle. I found the battery and starter to be in good shape so, I figured I'd look for something obvious before getting out the meters and vacuum pump.(I haven't done a thorough and official tune up on this truck for a long time (I guess, THAT'S kinda obvious, lol) and it hasn't given me any trouble for years!) 
Anyhow, while checking filters I approached the SECONDARY air filter (Also referred to as the Air Intake Ventilator filter) as I pried off the top WATER pours out! About a half pint of it! Of course, the metal encasement cage of the filter is all rusted so, it's been in there a while. I immediately checked for water in my oil, nope, thank god. I do live on the coast. I have a theory about what has occurred( And NO, my truck does no go moonlight surfing while I slumber, lol. ) but, I'd like to her YOUR ideas. Anyone?


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## octaneman (May 13, 2009)

Hi L olver


The first step is to give your engine a badly needed tune up then clear out any debris thats been trapped in the air filter box. If your truck is equipped with a MAF the salt water will destroy the sensor causing all kinds of problems, the first sign of a bad MAF is the engine RPM's will begin to oscillate. Pick up a can of decarbonizer from your local auto parts and clean out the the throttle body of any carbon deposits, if your engine is as bad as you say it is then its best to run seafoam through your engine to clear the carbon. Run the seafoam through your engine to see what effect it will have on performance, but make sure you follow step by step instructions on how to use it. 



post back your findings.


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## L olver (Feb 4, 2008)

Thank you, OctaneMan.
All good advice,well taken.
Any ideas on how all that water got into a sealed vacuum canister ? I checked all the vacuum lines with WD40 spray preliminarily, and found no leaks.


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## octaneman (May 13, 2009)

Without actually inspecting the engine any thoughts that I may have on it will be based on pure speculation. I'm basing my theory that since you do live on the coast, you drive around areas where waves hit creating a water mist which gets sucked into the intake. Over a period of time water collects in small areas in and around the engine where there is absence of air for evaporation.


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## L olver (Feb 4, 2008)

Thanks.
I wasn't testing you. Speculation is exactly what I'm hoping for. That is the only way that, I too have figured the water got there. That is, in the absence of going so far as to taste it for salt.


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## octaneman (May 13, 2009)

The best advice I can give is to install water absorption filters for your engine, at least it will provide some form of protection against water mist.


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## Midnight Tech (Dec 31, 2001)

L olver, 
The AIV box on the D21/WD21 series has a tendency to collect condensation and eventually the case will rust out. 
The system is hooked to the exhaust, and the moist air from the exhaust cools once it gets to the AIV filter. There is supposed to be a way for this condensate to drain out but it usually just pools in there and causes problems.
Go ahead and give the truck a good tune-up and see if things clear up with your starting problem.


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## L olver (Feb 4, 2008)

Thanks , to you both. 
Yes Midnight. The case did rust out. I intend to go at it with a wire wheel and lightly coat it with a grease. Also, the truck has had piecemeal tune-ups, just not done by a facility. And this truck faithfully passes California's tests too. It is VERY forgiving. But yes, that thorough tune up is on its way.
I have a secondary question for you, Midnight. My manual does not explain well what the ultimate function of this secondary filter is. Does it tie into the EGR, perhaps? It's difficult to see where the vacuum lines end up. 
Thanks much!


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## Midnight Tech (Dec 31, 2001)

Not familiar with the CA version other than what I've seen in the FSM, but the function of the hot/cold AIV is to provide extra air into the catalytic converter to more completely reduce emissions.
The cold AIV (which is what I have - Federal emissions) has 2 lines - one coming from the engine and another going to the center of the converter. CA uses a hot AIV but not sure of its plumbing at the moment. It does not tie into the EGR system.


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## L olver (Feb 4, 2008)

Aha...
Thank you, Midnight! Anymore information that anyone may have on this California system is welcome and much appreciated.


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## L olver (Feb 4, 2008)

I must correct the information I gave in the original description above... The AIV, I have read, stands for "Air Injection Valve" and the filter associated with it is what was rusted out with water. I am researching still and welcome any further info on the AIV system. Thanks.


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## L olver (Feb 4, 2008)

I found this and it seems to specifically target the specific cause of my AIV problem.

"WHY AIV(PAIR valve) IS A PROBLEM:

If reed valves become gunked up in the AIV unit, exhaust gas and condensation will be allowed to flow into the intake.(ie air box where air filter is). This can cause your cars idle to bob or drop below what it’s supposed to, also can cause slight stumble during acceleration. Deposits from exhaust can coat MAF and cause ECU to read the wrong amount of intake air flowing past it."


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## Jonathan99 (Apr 9, 2011)

Thanks for all the good info y'all, I live in Mississippi and nowhere near the coast but I also found the A. I. V. box on my '89 D21 completely rusted out. I was changing the plugs and wires, after a year of owning this truck,(my first vehicle) it was the first time I ever noticed the aiv box even though I've worked on the truck a good bit. Is it a difficult part to replace? Thanks,


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## Jonathan99 (Apr 9, 2011)

One more question, where can I find a replacement AIV box? do I need to replace the valves and whatnot inside the box? Is there a company that builds parts for the early Nissan's? Thanks, Jonathan


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## Midnight Tech (Dec 31, 2001)

Jonathan, is yours a hot or cold AIV unit?


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## Jonathan99 (Apr 9, 2011)

Man, I couldn't say. Could you give me a history of the AIV box? Do they just appear on some models? Does every vehicle have them and what should I look for in a hot vs. cold? Thanks


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## Midnight Tech (Dec 31, 2001)

Can you post a pic of what's left of your AIV on the truck?


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