# IACVU Removal and Cleaning with pictures.



## Catman (May 21, 2004)

Last week I removed the Idle Air Control Valve on my Sentra. It was full of carbon, and after cleaning it the car did not stall or hesitate when warm like before. So far, about a 75% improvement overall. In my enthusiasm, my first post was confusing. I am a little dyslexic, and words can get jumbled in my head. So, in the interest of clarification, I removed it a second time, took some pictures to outline the procedure I used. I am not a mechanic. Just a poor DIYer. I cannot say all info is accurate. I did use Alldata as a reference. I am showing you all I know. Before removal of the IACVU, I did try to adjust the idle. It did not help, so I set it back to where it was. I also tested the Auxiliary Air Control Valve using an ohmeter. It was supposed to be about 10 ohms. It tested at 10.5 ohms, so I assume it was OK. As a last resort, I removed the IACVU with great results. I think all the carbon that deposited on the spring caused the mechanism to bind, especially when the engine was warm, since after cleaning process it rarely stumbles or hesitates. I installed an aftermarket cruise control on my car. Ignore the extra cables, vacuum hoses, and the big vacuum reserviour. Hope this helps. This is my first time attaching pictures. Cross your fingers that is works!


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## fos160se (Oct 23, 2002)

No pic's yet - Please it would help me a lot because I plan to do it tomorow morning. If you can't post it send it to me [email protected] I realy need it before tomorow - thanks


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## Catman (May 21, 2004)

Sorry everyone. Brain overloaded. Was not able to get the pictures to display no matter what I did. I am able to email them. Will try to figure this out again tonight.


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## sno (Oct 4, 2002)

check out the newbie section to find out how to post pictures.


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## Catman (May 21, 2004)

*2nd try at post IACVU pictures*

Hope it works this time!


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## Catman (May 21, 2004)

Picture 0001 is the location, looking at the front of the engine, it is one the left side of the intake manifold.

Picture 0003 I am removing removing the wiring harness. I just sqeezed and moved the clips back and forth, then they pulled out. Then removed three bolts, and last removed the hose coming out of the bottom. 

Picture 0006 is the AACV turned on its side. The top part with the purple plastic connector is the fast idle control solenoid valve. I did not mess with it. Alldata did not show how to test it. You can check the resistance of the AACV with an ohm meter across these two terminals (in the reddish brown plastic). It should read approximately 10 ohms. There are two small screws that hold this AACV to the entire unit. It has a plunger and a spring (the section with the lettering). You are supposed to be able to pull it out to see if the spring is broken. I could not get mine out, but it moved freely and the spring seemed to work. So, I just put it back together. This plunger pushes against what looks like another plunger, diaphram, and spring that is exposed to the carbon in the intake. That was filthy and binding. 

Picture 0009 shows the spring after it was cleaned. Used throttle body cleaner and a toothbrush. Was careful not to use anything sharp. It looks like it has a diaphram that could be punctured. After cleaning, blew it dry with air. Seemed to move freely.

Picture 0029 shows all the crud in the intake manifold. I had some high temp RTV, so I coated the old gasket with a thin coat. Was able to get a good seal both times I installed it. Torqued to 5 ft. lbs. Used a 10 mm socket with a short adapter.

Put everything back together reverse of the way I took it off. This is on the 1.6 motor. I have no idea what it will be like on the 2.0 motor. I plan to clean this unit again during my next 30,000 mile throttle body cleaning, since it is exposed to similar carbon deposits. Hope that helps.


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## Catman (May 21, 2004)

One last thing. Thanks for your patience. Guess I was tired last night. Had good intentions, but 2 hours after I took these pictures on Monday a storm came through that blew down trees and limbs. No power for three days. Better late then never. Enjoy!


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## Catman (May 21, 2004)

*There is a test for the Fast Idle Control Solenoid*

I stand corrected. I double checked and Alldata did show how to test the FICD. Supposed to apply battery voltage to the terminals after disconnecting the harness. You should here a clicking sound. If not, then you can remove the solenoid (it looks like it unscrews) and check for a sticking plunger or broken spring. If it fails the above test it needs to be replaced. I did not check mine, but since it is running so well, I may skip that step. Just didn't want to mislead anyone in case your FICD is bad.


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## bast525 (Jul 3, 2004)

Thanks for that! Been hoping someone would post something like this since I first signed up here  

Too bad for me that this is a 1.6 though... I have the 2.0 and the placement is a little different. Still on the left hand side of the manifold, however it's a bit lower down in the engine bay, and there are A/C hoses/pipes and I believe a power steering hose running in the way of it... VERY hard to get to for me. So I've been kinda afraid to try it. Gonna take another look today and really try to plot out exactly how to get to the bolts and get everything and be sure I can get it back in.


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## fos160se (Oct 23, 2002)

Thanks for the pictures, at least I know how the unit looks like. I tried to take it off Saturday morning but couldn?t get to the unit because I got the hi port motor SR20DE and to make things worse its also right hand drive which mean that the brake booster is in the way. I tried but couldn?t even get the 10mm in there , whish my hands were as small as a six year old.


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## gimmiedecay (Jul 14, 2004)

thank you catman,your motivation has inlighted me,i will drink a beer to that.


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## danifilth (May 14, 2003)

yes catman thank you I cleaned mine yesterday with your help.Hope you get some good rep.


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## jareh80 (Jun 5, 2005)

*cleaning*

Catman i to give thanks for the info;now time to see if that was the problem.


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## Catman (May 21, 2004)

jareh80 said:


> Catman i to give thanks for the info;now time to see if that was the problem.


I gave it my best shot. Since then I have learned a lot more. If the info helps another person, it was worth the effort.


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## jareh80 (Jun 5, 2005)

*i thanke ya*

It help ;and i thank ya...


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## Novelist (Jul 7, 2004)

*Other cause*



Catman said:


> Last week I removed the Idle Air Control Valve on my Sentra. It was full of carbon, and after cleaning it the car did not stall or hesitate when warm like before. So far, about a 75% improvement overall. In my enthusiasm, my first post was confusing. I am a little dyslexic, and words can get jumbled in my head. So, in the interest of clarification, I removed it a second time, took some pictures to outline the procedure I used. I am not a mechanic. Just a poor DIYer. I cannot say all info is accurate. I did use Alldata as a reference. I am showing you all I know. Before removal of the IACVU, I did try to adjust the idle. It did not help, so I set it back to where it was. I also tested the Auxiliary Air Control Valve using an ohmeter. It was supposed to be about 10 ohms. It tested at 10.5 ohms, so I assume it was OK. As a last resort, I removed the IACVU with great results. I think all the carbon that deposited on the spring caused the mechanism to bind, especially when the engine was warm, since after cleaning process it rarely stumbles or hesitates. I installed an aftermarket cruise control on my car. Ignore the extra cables, vacuum hoses, and the big vacuum reserviour. Hope this helps. This is my first time attaching pictures. Cross your fingers that is works!



Thanks for the pictures.
I located mine (1.6 same as yours) quickly enough, removed the whole assembly then stripped it down. The spring etc, was pretty clean so I reassembled it and put it back on the motor. Problem was still bad; idle was 'all over the place', car drives OK but every time I had to stop, it would stall. (Auto box) I had to drive with both feet so I could give it some gas every time I stopped, or it would stall.

So I went around the engine pulling gently on all the sensor wires to see if there was an intermittent.
On the other side of the block - the intake side - I found a black box sensor between the air filter and the intake. When I gave this a tug, the idle jumped up and immediately settled down purring like a sewing machine. I tried removing the sensor connector and the engine revs jump up quite a lot, plug it back in and it revs for a moment then settles down nicely.
Since this, my 1.6 drives really nicely, no stalling whatsoever.
I have no idea what this sensor is but it evidently has a BIG effect on the idle and general running of the engine, so this would be the one to go for in my humble opinion.
Clive


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## Novelist (Jul 7, 2004)

*Other cause*



Catman said:


> Last week I removed the Idle Air Control Valve on my Sentra. It was full of carbon, and after cleaning it the car did not stall or hesitate when warm like before. So far, about a 75% improvement overall. In my enthusiasm, my first post was confusing. I am a little dyslexic, and words can get jumbled in my head. So, in the interest of clarification, I removed it a second time, took some pictures to outline the procedure I used. I am not a mechanic. Just a poor DIYer. I cannot say all info is accurate. I did use Alldata as a reference. I am showing you all I know. Before removal of the IACVU, I did try to adjust the idle. It did not help, so I set it back to where it was. I also tested the Auxiliary Air Control Valve using an ohmeter. It was supposed to be about 10 ohms. It tested at 10.5 ohms, so I assume it was OK. As a last resort, I removed the IACVU with great results. I think all the carbon that deposited on the spring caused the mechanism to bind, especially when the engine was warm, since after cleaning process it rarely stumbles or hesitates. I installed an aftermarket cruise control on my car. Ignore the extra cables, vacuum hoses, and the big vacuum reserviour. Hope this helps. This is my first time attaching pictures. Cross your fingers that is works!



Thanks for the pictures.
I located mine (1.6 same as yours) quickly enough, removed the whole assembly then stripped it down. The spring etc, was pretty clean so I reassembled it and put it back on the motor. Problem was still bad; idle was 'all over the place', car drives OK but every time I had to stop, it would stall. (Auto box) I had to drive with both feet so I could give it some gas every time I stopped, or it would stall.

So I went around the engine pulling gently on all the sensor wires to see if there was an intermittent.
On the other side of the block - the intake side - I found a black box sensor between the air filter and the intake. When I gave this a tug, the idle jumped up and immediately settled down purring like a sewing machine. I tried removing the sensor connector and the engine revs jump up quite a lot, plug it back in and it revs for a moment then settles down nicely.
Since this, my 1.6 drives really nicely, no stalling whatsoever.
I have no idea what this sensor is but it evidently has a BIG effect on the idle and general running of the engine, so this would be the one to go for in my humble opinion.
Clive


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## Catman (May 21, 2004)

Clive, sounds like you are onto something. I guess a lot of things could affect idle. For me, after a year, the cleaning of the IACV resolved my stumbling issue. Idle was OK before and after, for the most part. So maybe your problem is a little different, and needed a different solution. Glad to hear you resolved your issue. I am a novice regarding cars, so I just passed on my experience. Pretty limited, but maybe helpful for some. Take care.


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## tmcnally (Jun 23, 2005)

Catman said:


> For me, after a year, the cleaning of the IACV resolved my stumbling issue.


My car's idle would drop whenever I let off the gas to almost the point of dying...I just did this procedure and the car runs awesome!!! Great writeup. FYI...I used brake cleaner and that worked well also. Also, if you cover some of the holes with your fingers you can 1/2way fill the cavity with cleaner...then just shake the *^&% out of it filled...ALOT of junk comes out that way quickly.

:thumbup:


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## Catman (May 21, 2004)

tmcnally said:


> My car's idle would drop whenever I let off the gas to almost the point of dying...I just did this procedure and the car runs awesome!!! Great writeup. FYI...I used brake cleaner and that worked well also. Also, if you cover some of the holes with your fingers you can 1/2way fill the cavity with cleaner...then just shake the *^&% out of it filled...ALOT of junk comes out that way quickly.
> 
> :thumbup:


Thanks for the tips. I really was on a strong learning curve when I cleaned my IACV, so the additional info is helpful. I just had emissions done. Passed with all reading way below what was necessary. I still have the original cat. Car starts right up, no stumbling, and running great. I am very impressed with these little engines. At 176,000 miles, it runs like a new motor would. A little TLC goes a long way with this motor.


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## jamescroy9 (Feb 16, 2008)

Catman said:


> Last week I removed the Idle Air Control Valve on my Sentra. It was full of carbon, and after cleaning it the car did not stall or hesitate when warm like before. So far, about a 75% improvement overall. In my enthusiasm, my first post was confusing. I am a little dyslexic, and words can get jumbled in my head. So, in the interest of clarification, I removed it a second time, took some pictures to outline the procedure I used. I am not a mechanic. Just a poor DIYer. I cannot say all info is accurate. I did use Alldata as a reference. I am showing you all I know. Before removal of the IACVU, I did try to adjust the idle. It did not help, so I set it back to where it was. I also tested the Auxiliary Air Control Valve using an ohmeter. It was supposed to be about 10 ohms. It tested at 10.5 ohms, so I assume it was OK. As a last resort, I removed the IACVU with great results. I think all the carbon that deposited on the spring caused the mechanism to bind, especially when the engine was warm, since after cleaning process it rarely stumbles or hesitates. I installed an aftermarket cruise control on my car. Ignore the extra cables, vacuum hoses, and the big vacuum reserviour. Hope this helps. This is my first time attaching pictures. Cross your fingers that is works!


I own a 1996 Nissan 200SX with a 1.6 liter engine, manual trans. 144k miles.

Symptoms:
I was having the same problems:
1) Come to a stop, depress the clutch. The RPM's dip down to 400 and the engine feels like it's about to quit. 2 seconds later, the engine recovers to 700 rpm.
2) With the A/C on, come to a stop, depress the clutch. #1 will happen. While sitting at a long light with the clutch depressed, waiting for the light to turn green, the A/C cycles. When the A/C turns on, the engine rpm increase to around 1,100 rpm. This is good. Then the A/C compressor turns off, the engine rpm's drop below 400 and the engine stalls and quits right there while you are waiting for the light to turn green. You have to start the engine again so you can continue to wait until the light turns green.
3) Idle is rought, but stays around 700 rpm.

1st try at fixing the above symptoms:
1) Replaced:
a) Spark Plugs
b) Rotor
c) Distributor Cap

2nd Fix after reading 'fixes' from this quorum:
1) Took the throttle body off of the intake manifold. Looked at the butterfly valve that lets air get into the air intake. There were all kinds of carbon on the back-side of the butterfly valve (the side that connects to the air intake). The side of the butterfly valve that was facing the air cleaner box wasn't too bad, however, there was some carbon there too.
2) Totally removed the whole throttle body and sprayed with carb cleaner. Removed all carbon gunk. 
3) Put throttle assembly back on air intake, tested it out. Works like a champ now. Symptom #1 and #2 above are no longer an issue. Coming to a stop and depressing the clutch, the engine rpm stays around 800 and never dips below.
4) Idle is smoth now.


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## chrismariscal (Jan 10, 2011)

Thank you catman.
you're my hero.


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## chrismariscal (Jan 10, 2011)

Hello all, 
Ever since i cleaned the IACVU, my cars been giving me problems starting and idling.
And i know its all because i messed with the Idle Screw.
I took a picture of what mines looks like now. Could anyone please take a picture of theirs and share it with me, or really all of us so i can see how far in/out the screw is supposed to be?
Thanks a lot!
Again, here is what mines looks like now:


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## jdg (Aug 27, 2009)

You don't set the idle screw (otherwise known as a minimum air screw) by setting it "3/16 inch down from the lip" or "four turns out from lightly seated".
You set the idle screw by reading the directions in the manual (Haynes, Chilton, FSM, etc) on how to put ECU into "timing/idle rpm adjust mode".
Then, you set the timing, then you set the idle, then you recheck the timing, then you recheck the idle.
Or you can mess around and play with it for a few months until you get it set right.
Your call...


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## chrismariscal (Jan 10, 2011)

Ahhh i found it! Thank you so much!
its on EF & EC page 220.


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## SE_RBOY (Jul 28, 2010)

I tried cleaning my iacv with throttle body and air intake cleaner and nothing really happened.... will try to clean it with carborator cleaner and see what this does. on cold starts in the mornign its fine but in the afternoon after its been in the sun it will run in park but after i throw it in gear it will stall only if i dont let it warm up first before i move.


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