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jjonez

What's this thing?

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IMG_20180512_185008626.jpg

 

It's crumbling away on the bottom and leaking some kind of fluid.

 

Today after I changed my oil and was driving home the truck started to stumble and was wanting to die. Of course I was freaked out cuz I thought I had screwed something up during the change. After I shut it off it took a long extended crank to get it start again. For the most part it still runs and drives fine, except now it idles slightly higher (1000 now vs 750 before) and if I quickly blip the throttle from idle it'll stumble and almost die before picking itself back up. If I ease onto the throttle it revs like normal. Sometimes when I would get deep on the throttle while driving the same kind of stumbling would occur. Could the leaky thing in the picture be the culprit? There's a vacuum line coming off it going to somewhere on the intake so I figured it's a good place to start. I'll admit I'm kind of embarrassed I have no idea what it is haha. Thanks for your input!

 

 

IMG_20180512_185053923.jpg

 

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More food for thought. The thing is also connected indirectly with a Y to what I just learned is the anti-backfire valve. While I was driving home it backfired a couple more times and louder than usual, and the smell of gas was pretty pronounced after I parked and was idling.

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Posted (edited)

The '89 manual shows that as an "A.I.V. Box (For Hot A.I.V.)." It connects to the exhaust system and to manifold vacuum, so if it's rusted through at the bottom, it could be allowing unmetered air into the intake manifold (raising the idle and screwing up your fuel mixture).

 

The anti-backfire valve is supposed to dump air into the intake when there's too much vacuum (apparently the suction on deceleration pulls too much fuel through the injectors and makes the engine run pig rich and backfire otherwise). Looks like if you take the air filter out, there's a small pipe to the driver's front of the throttle body, coming up through the bottom plate of the air cleaner. Cover the end with your finger, rev to 3k, then let the throttle snap shut and you should feel a little suction from that port. If you feel suction, the valve is working.

If the AIV and AB share a vacuum feed, and the AIV is leaking air into that feed, the AB valve wouldn't see full manifold vacuum and so wouldn't do its job.

Edited by Slartibartfast

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Posted (edited)

Thank you! Googling the part found this thread from a few years ago:

 

http://www.nissanpathfinders.net/forum/topic/37076-air-injection-valve-aiv/

 

Same rust underneath, but no one mentioned any performance issues from it. I hope this is all it is. It's an expensive part, and probably will be hard to find in a JY. Any idea what the fluid leaking out could be? *Edit* from another thread I found I guess it's just water, maybe condensation build up or something. Explains the rust (duh).

 

Lucky me it passed smog a week before this started happening. But it was such a sudden onset, the engine was running completely fine up until saturday

Edited by jjonez

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So glad I don't need to pass emissions test here.

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It is the A.I.V system. There's a reed valve and an air filter inside. These filters tend to be out of sight and out of mind so they're not changed routinely as they should. They can become clogged (probably mostly from just rotting over time). I would imagine at some point they may cause some problems. I can could send you the pages from the FSM, but you may have to PM me and send me a email as I don't think we can "paste" them on the forum.

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Yeah, getting an early EFI past smog does not sound like fun.

 

If it's just the can that's rotten, and the moving parts are still alright, I'd just pull the can out, clean up the worst of the rot, and then patch the hole with something. You could weld/braze/solder, but I'd be concerned about messing up the rest of the assembly (unless that cover comes off easily). I'll bet you could get away with covering a small hole with epoxy putty, JB weld, Bondo, something like that. Cut a piece of a can if you need to cover a big hole.

I hadn't seen the filter in there! Definitely give that a good clean (or a new one if it's available) while it's open.

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Fiberglass the hole.

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Thanks for the suggestions guys. I'll start by cleaning up the hole/filter and patching it. Maybe try carbon fiber epoxy since it's handy at work. Unfortunately I won't be able to address it until next weekend but I'll be sure to update when I do.

 

I'm fortunate, the pathy passed well above the margins without me having to fix anything. Hopefully that continues in the future.

 

August59, if the simple patch doesn't work out I might hit you up for those fsm pages. Thanks!

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As long as the cat/egr are working, these trucks breeze through emissions tests. At least both of mine do.

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DLZfUZ9.jpg

 

Yuck. I hit the junkyard without much success. Found one 86 v6 hardbody with the part already pulled, and another hardbody with the Z24 that uses the same part. But this one was in even worse shape than mine. I went ahead and ordered a brand new $200 part from courtesyparts, but based off my experience trying to get a new oil sender, I'm more than half expecting to get an email saying they don't actually have the part anymore. Mine is dried out now and doesn't look as nasty, so if the new one doesn't work out I'll look into cleaning this one out.

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Wow! That's nasty. Looks like something laid eggs in there! Hopefully the new one works out.

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He lives!

 

IMG_20180603_100851466.jpg

 

IMG_20180602_141949130_HDR.jpg

 

Parts arrived early and I wasted no time installing. I purchased part no. 14812-12G15

 

here: https://www.courtesyparts.com/oem-parts/nissan-case-eai-valve-1481212g15

 

Pricey, but I was pleasantly surprised that it did in fact come with everything pictured, the reed valve, case, and new air filter. Who new a 30 year old part could looks so good? After I got it installed and started it up I was still getting occasional hiccups and it would stumble pretty bad when I opened the throttle. After warming up and driving around a bit, everything was totally fine and this morning it cold-started completely normal. So I'm chalking up yesterday's cold start to not having been run in 3 weeks and the ECU resetting after having the battery disconnected.

 

Hopefully that's the end of it. I'm definitely going to keep an eye on this new one and clean it periodically.

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Welp, I guess the AIV wasn't the culprit and I'm looking at an intermittent issue. Today as I was creeping up the freeway on ramp in traffic the truck started to sputter then died. It cranked fine but wouldn't turn over. Luckily within a minute some good samaritans helped push it out of the way before my fellow commuters could get really pissed.

 

After a loooong crank the engine finally caught but had the same issues stated earlier in the thread. Slightly higher idle, stumbling and almost stalling when tapping the throttle from idle or giving it heavier throttle while driving.

 

After a bit more driving now of course it starts and runs fine. Which makes this way harder to figure out, but I'm guessing a fuel or air issue.  Any suggestions on where to start? Thanks guys!

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Side note: I pulled off the brand new air induction valve/air cleaner assembly and it already has collected A LOT of water in it after less than 700 miles.  I'm already seeing some corrosion on the perforated metal filter backing. Is this just what these things do or am I missing something here?  Possibly related to my current issue i.e. water getting sucked into the intake somehow?

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My former 87 Hardbody never passed emission tests on it's own, with full emissions, cat and everything. I heard way back, not sure if it was true that Nissan rushed the VG30i into production and is why they had emission problems ??

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Your issue sounds like the typical distributor module problem. That's the only problem I ever had with my factory set up. Mine would just be really hard to start once it was warm but ran pretty normal once it was running, just don't turn it off! I'd have to crank it for minutes to get it to start when it was hot! Almost left my ass 5 miles back in the woods one time!

James

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10 hours ago, JamesRich said:

Your issue sounds like the typical distributor module problem. That's the only problem I ever had with my factory set up. Mine would just be really hard to start once it was warm but ran pretty normal once it was running, just don't turn it off! I'd have to crank it for minutes to get it to start when it was hot! Almost left my ass 5 miles back in the woods one time!

James

 

Supposedly you can upgrade to the 95 version which is not problematic at all. Though I guess that's not an issue for yours now lol

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Thanks for the replies. Mine passes CA emissions just fine even when it had the rotted AIV box, I just don't get why it fills with water so easily.

 

In this case the truck is only hard to start the first time after the stumble and die, then it runs funny with the symptoms mentioned but still warm starts better than any vehicle I've owned. Half a crank and it explodes to life.

 

So far the issue has occurred twice, this most recent time it died, was hard to start, ran funny, and then worked itself out 15 minutes later. It currently starts and runs as normal but I'm just waiting for the next occurrence.

 

I've read a little bit about the head temp sensor, but it doesn't match my symptoms exactly and I don't show a code for it.

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Ok, so maybe it's the coolant temp sensor after all.  The issue came back worse than ever today after I did some poking around under the hood.  I pulled a spark plug and it had heavy fresh carbon deposits on it as well as inside the cylinder and the tailpipe (I checked the tailpipe recently and it was pretty clean).  Also it looked like the throttle body butterfly had a thin layer of fuel just sitting on top of it.  Can this sensor cause the injectors to dump excess fuel?  I checked the ecu again and this time of course it showed 13, so I hope replacing the sensor is all it takes.

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The temp sensor is one of the things the ECU uses to determine fuel mix. A cold engine needs a richer mix. So, yeah, a problem on that circuit could definitely be causing it to run rich.

 

How tight is the connector on the temp sensor? I solved an intermittent stalling issue on mine just by tightening up the plug on one of the idle air components. I used something pokey to sort of squish the female connector pins a little tighter so they'd grip the male pins better. The connector felt pretty loose when I checked it, and much tighter afterwards, and the truck hasn't stalled at idle since.

 

Weird that the new valve is already taking on water. I'd be tempted to drill a small hole in the bottom of the casing (smallest bit you've got) to allow it to drain. Where's it coming from? :scratchhead:

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Yea after I wiggled the harness a bit the resistance went from something like 5k ohms to 3k ohms then the truck ran fine.  I went ahead and ordered a new sensor/sub harness just to be thorough.  The AIV box has a spiraling channel along the outside that looks like it's supposed to drain out water, but apparently not well enough.  An additional hole straight thru might be a good idea.

 

I'm also thinking of just removing the AIV stuff between smog checks to keep it fresh.

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Installed the new sensor/harness today.  Also changed the oil cuz I'm paranoid.  The truck was running fine before and after the install.  Hopefully I can officially put the lid on this and not reopen this thread again a month from now.

 

Oh and this thread was really helpful in getting at the sensor.

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