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IACV Preventative replacement


PathyGig12
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Hey guys

 

So I know there are some threads about this topic but I’d like to get the current consensus and most up to date info that the community has. 
 

My plan is to swap out my IACV before it goes bad because I have 285K in the original part and I know it’s famous for taking the ECU down with it when the resistance drops too low in the motor. My question for you guys is which manufacturer would you recommend and what the processes is for re-teaching idle afterwards (or if this is even necessary if the part is swapped while still in good working order). How many success stories are out there, any bad failures after a swap? Specifically when the part is being changed preventatively. Every post I saw when researching this part has involved replacement after failure and a need to repair the ECM at the same time 

 

Edit to add:

 

I’ve heard mixed reports on the Hitachi part, but I always thought that it was OEM? How could it be worse than the OEM part which costs $200 if they’re both made by hitachi? I already have the hitachi sitting in the garage and don't want to resell it and look for a nissan OEM if they both have the same chance of failure

 

Oh yeah and one more thing. I noticed that the Motor is a separate piece, is there a way to swap just the motor since that’s the part that will fail? Or maybe even rebuild it? I saw some ebay sellers of what looks like the motor but can’t find a part number on rock auto

Edited by PathyGig12
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My understanding of the problem is not that the IAC motor fails and goes low resistance, it's that the coolant passageways near the IAC (to prevent throttle plate and IAC icing) corrode and let coolant get into the IAC motor, which subsequently shorts the motor out and presents too low of a resistance to the ECU driver, which is not properly protected electrically.

 

Before my Pathy engine died of lifter death, instead of replacing my IAC, I was just going to bypass the coolant loop through the throttle plate. In those threads you should have seen several references to people successfully doing this without issue. In theory you could run into a throttle icing problem, but no one has reported it. Unless you are in a very cool and humid environment I doubt you'd have a problem.

 

Hitachi is the OEM for many parts on Nissan, but I'm not sure for the IAC. Who was saying bad things about the Hitachi IAC? Did they for sure buy it from a reputable source and not a 3rd party Amazon seller that stuck a fraudulent label on it? I've used a good number of Hitachi parts including coil on plugs, and alternators, and haven't had a problem.

 

You should have zero problems if you want to replace it preemptively, install it correctly, and use a OEM or Hitachi part. You do need to run the idle air relearn procedure. After this many years there is almost 0 chance that a new part has the same electrical characteristics as your old one. Do you have the service manual? It has the procedure in there.

 

If the above is correct, then replacing only the motor wouldn't make sense. 

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Hey thanks man, that’s some good info there.

 

It does leave me a bit confused though. Number one, is this issue isolated to the nissan VQs, or do other engines run coolant through their IAC valves as well? In either case, why would the part be made of something susceptible to corrosion by coolant if it was designed to run this way? I’m not talking about the motor by the way, I’m talking about whatever part of the valve is being corroded and allowing coolant to get to the motor. And on top of that, does this mean that regular cleaning of the IAC wont help to stop the issue with corrosion?

 

Number 2, would a gasket change offer the same protection as swapping the entire part? Is the gasket keeping the coolant out or is it the metal structure of the unit that keeps the coolant from getting into the motor? If so, which gasket? Surely not the one around the edges that keeps air out?

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Hey thanks man, that’s some good info there.
 
It does leave me a bit confused though. Number one, is this issue isolated to the nissan VQs, or do other engines run coolant through their IAC valves as well? In either case, why would the part be made of something susceptible to corrosion by coolant if it was designed to run this way? I’m not talking about the motor by the way, I’m talking about whatever part of the valve is being corroded and allowing coolant to get to the motor. And on top of that, does this mean that regular cleaning of the IAC wont help to stop the issue with corrosion?
 
Number 2, would a gasket change offer the same protection as swapping the entire part? Is the gasket keeping the coolant out or is it the metal structure of the unit that keeps the coolant from getting into the motor? If so, which gasket? Surely not the one around the edges that keeps air out?


Many cars have coolant flow near the idle valve along with the throttle plate. While leaks into other makes of idle valves happen, the VQ seems particularly prone.

I haven't done mine and it's been a long time since I have seen the pics of what it looks like. But everything in a car is corroding at a certain rate. Manufacturers decide on how expensive of alloy to use or how many gaskets or seals to use on a cost benefit analysis. And the ECU has no protection to a short on the IAC drive. This was particularly stupid of Nissan.

Doing a gasket change and inspection might work. As stated I haven't done mine. At that point I'd just try the bypass. Anything I do I try to do only once and make permanent, unless it's a wear part. But if you have a Hitachi part in hand that isn't returnable, and +200k on your truck, it seems like a no brainer to throw it in there, learn what it looks like, inspect it, and drive, along with a coolant flush. There is almost no way this will cause the eventual end of your truck.

Probably if one replaced their antifreeze every 2 years using good antifreeze with corrosion inhibiters and distilled water, this would almost never happen. But honestly in 10 years I never even changed mine. But cleaning the IAC wouldn't do anything.

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I recently bypassed the coolant on mine while changing the spark plugs. I just used a 3/8 brass "hose mender" with the stock hoses and zip tied it out of the way. Using a single piece of hose would be better but the back connection looked rather difficult to get to. Easy enough to do for the peace of mind.

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The coolant doesn't actually go through the IAC valve, it goes through the throttle body. Problem I have seen is the line leaks and drips onto the IAC motor causing corrosion. That leads to higher current required to operate and that is what burns out the drivers in the ECU. With the Pathfinder, the problem is only on a couple years. It is only on the 3.5 with a cable operated throttle. 

I would feel perfectly comfortable installing a Genuine Hitachi unit, pretty sure that is the manufacturer for the original. I suggest replacing the coolant hoses or bypassing the throttle body while in there to prevent the problem. 

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Thanks for weighing in guys, I appreciate the responses. 

 

I guess this week I’ll try to throw on the new one and hope for the best. Being in Colorado and it’s almost winter, I don’t like the idea of bypassing the throttle body but  I could always do it as a sort of seasonal thing maybe? That would at least double the life of the new IAC 

 

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The cold dry air of Colorado is perfect to prevent or reduce the chances of throttle plate icing. New Orleans in the winter would be the worst for it, where the air is full of moisture and its near freezing so the air temp drops and the water condenses to ice just as it crosses the the low pressure zone of the plate. But some experimentation will let you know if it will be a problem for you.

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  • 2 years later...
On 9/29/2020 at 12:14 AM, Mr_Reverse said:

The coolant doesn't actually go through the IAC valve, it goes through the throttle body. Problem I have seen is the line leaks and drips onto the IAC motor causing corrosion. That leads to higher current required to operate and that is what burns out the drivers in the ECU. With the Pathfinder, the problem is only on a couple years. It is only on the 3.5 with a cable operated throttle. 

I would feel perfectly comfortable installing a Genuine Hitachi unit, pretty sure that is the manufacturer for the original. I suggest replacing the coolant hoses or bypassing the throttle body while in there to prevent the problem. 

 

 

Based on this guy's video, a seal fails internally it sounds like and shorts the motor out.  From what he says this comes from the coolant passage flowing through the IACV, but you seem to think that is not the case. So you are saying it comes from an external leak that drips onto the motor itself?  Can you identify the culprit hoses within the video?  Are they visible within the video? 

 

 

2002 Nissan Pathfinder Throttle Chamber Diagram

 

Based on this schematic I would guess the guy in the video is referencing that o-ring seal (16076MA) between the IACV motor and the rest of the part body.  I always thought, and maybe others as well, it was the gasket connecting the entire IACV unit to the throttle-body that failed (16076M).  If anyone can confirm or deny any of my assumptions, that would be greatly appreciated.  I'm also trying to prevent this from happening in the first place as I can find myself in some pretty desolate places where peace of mind is a beautiful thing.  

Edited by cham
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  • 3 weeks later...

The o-ring is an air seal for the idle control valve. Coolant doesn't normally come in contact at all. It simply has a small passage around the Venturi zone in the throttle body to prevent icing in cold moist conditions. The hoses are the 2 small rubber hoses that go to the throttle body, when they leak, the coolant drips onto the outside of the idle valve and intrudes over time generally at the electrical connector. 

 

This problem is found only on the VQ35, the VG33 doesn't have this problem. 

The picture you have posted is for the engine with the throttle cables, so the IAC is subject to the problem that the drive by wire throttle body doesn't suffer from.

Edited by Mr_Reverse
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The leaking of coolant from one compartment to another is seepage failure of this thin preformed O ring type gasket.

About 3 years ago i found coolant was getting sucked into the Idle Speed Control Solenoid chamber (i know that's not the name Nissan gives it

 (Idle Air Control Valve IACV) but it is better suited for the description) causing corrosion on the brass seating point for the solenoid plunger.

Causing idle issues. I guess I was l lucky to catch it before it had chance to short out the solenoid and then the ECM.I cleaned everything up including the brass seat area, installed a new seal and all worked for about 3 years.

Just last week the pathfinder woulndt start unless i open throttle more..it appears coolant is once again seeping into the wrong part of the chamber,

After driving for a few blocks all appears to work ok and the car idles fine and restarts fine.

But im guessing after i park it again and pressure from the cooling system once again will push coolant into the chamber past this faulty wimpy seal causing issues at next startup.

Since aside for this leak everything runs very smooth for a 2002 pathfinder with 197k.

This nissan has been a better vech than my Honda accord and Toyota van..

So when i get some time im going to do the bypass of the 3/8 coolant hose since i dont live in freezing area.

 

oh, ive heard from this leaky seal coolant can sometimes ALSo be seen leaking outside and can get the electrical connector to the IACV, even though the connector should be sealed and not allow liquid in perhaps with age it can.

 

idle body1a.jpg

idle body2a.jpg

idle body3a.jpg

Edited by lookingatyou2013
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  • 2 months later...
On 1/21/2023 at 11:21 PM, Mr_Reverse said:
The o-ring is an air seal for the idle control valve. Coolant doesn't normally come in contact at all. It simply has a small passage around the Venturi zone in the throttle body to prevent icing in cold moist conditions. The hoses are the 2 small rubber hoses that go to the throttle body, when they leak, the coolant drips onto the outside of the idle valve and intrudes over time generally at the electrical connector. 
 
This problem is found only on the VQ35, the VG33 doesn't have this problem. 
The picture you have posted is for the engine with the throttle cables, so the IAC is subject to the problem that the drive by wire throttle body doesn't suffer from.

@Mr_Reverse Are the red and blue circled hoses in the attached photo the correct rubber hoses you are referring to that leak?  Yes I do have the drive by cable operated throttle body.  


Edit: Just realized I do not have that hose circled in blue, just the red hose since mine is a 2002 and not a 2001 like in the video.

cc6687fae499fddbf6f5937db10a7ca9.jpg
Should I also go ahead and replace the hoses going to the IACV body at the green and yellow circled locations?

Lastly, is there any chance the throttle-body/intake gasket (16293M) might leak coolant onto the solenoid? I’m assuming coolant doesn’t come into contact there but just to clarify I’m curious.

@lookingatyou2013 When you mention the preformed O-ring type gasket that you replaced are you referring to (16076M) or (16076MA) from the diagram above in my past replies?


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Edited by cham
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  • 3 weeks later...

Was sitting in a drive through today when randomly my RPMs started to surge and held a constant 1000RPM (vehicle in Drive and foot on brake); shifted it into park and the RPMs went up to a constant 1500RPM.  This lasted about 5-8 minutes and then randomly they just decided to come back down to normal conditions.  I literally was planning on replacing the IACV gaskets and coolant hoses tomorrow as preventative maintenance, and I've never had any problems with idle so this was new to me.  If anyone can weigh in here, does this sound like a soon to be failing IACV?  No codes to speak of.  I will say the temperatures here in VA shot up today comparatively to previous weeks.

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If you were going to replace the ICV and hoses anyway, I would just take the intake apart and check for traces of coolant leaking or dripping around that area. From the previous posts it sounds like when this problem manifests, the car doesn't idle, which I interpret as stalling instead of revving up, but if you are concerned you should inspect around the ICV.

 

I just hope the 2003+ throttle-by-wire models are really unaffected because I've never even bothered to check mine.

Edited by EricCR
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