Index of all Tutorials

REMOVING AND CLEANING IACV UNIT:

INTRO: The IACV unit is easy to remove. 4 10mm bolts. Reach in at back of engine by firewall on passenger side. No need to remove intake manifold. Pictures are just for illustration. Very easy to disassemble. Make sure you find the plastic piston and spring. This is what needs cleaning.

DETAILS OF REMOVAL: The connectors have staples. remove the blue connector first. the yellow connector can be removed after you take bolts out and hose off of metal intake tube. make sure you reconnect 3/4 in inch diameter hose and yellow connector first when reinstalling iaa unit. black tie on ficd is reuseable. You will likely find that the aac valve is clogged with carbon mud.(easily comes off carb cleaner). You will have to remove epoxy off brass screw to remove it.(some years dont have this large brass screw). Be careful not to damage threads and slot for screwdriver. The brass screw can tighten or loosen the spring that shuts aac valve. It is best to screw the big brass screw clockwise at first because threads are filled with epoxy. You can then clean the threads and brass screw will unscrew and come off so you can clean the valve.















TESTING ELECTRICAL ASPECTS OF IACV UNIT

Ensure unit grounded properly. The metal contact between the unit and the engine is the ground. A wire from metal part of iacv to engine would provide a second ground. Make sure car is grounded properly too. What is resistance reading between negative battery post and engine chasis. Resistance should be low for there to be good ground.

2 wires from FICD solenoid(blue plug) :

First wire: black from solenoid to connector at front of engine. becomes green at connector and goes to diode(|<). continues green after diode and goes to green/yellow where it splits. one branch goes to slot 45 on eccs unit. the other branch goes to ambient switch which goes to ground when switch is closed.(reads open to gound)

Second wire: Red from solenoid to connector at front of engine.becomes blue after connector and goes to a/c relay.(reads open to ground)

2 wires from AAC solenoid(yellow plug):

First wire: Red/white from solenoid to connector at front of engine. changes to light blue and goes to 113 on eccs unit.

Second wire: red/green from solenoid to connector at front of engine.changes to brown and goes to positve at fuse box.

(the connector at front also has two wires from air regulation solenoid. blu/red changing to black/yellow and blue/white changing to black. the black wire goes to ground and reads 3.5 ohms)

(the connector is right at front of engine so it is easy to access.. The winding resistance should be 10 ohms for the aac valve/solenoid. you could apply voltage to solenoids to see if they work , also) My car does not have air conditioning so no point checking ficd. Testing the AAC(auxiliary air control): A. Check overall function1. start engine and warm it up2. check idle speed- should be 700 -+ 50(if no good, adjust)3.perform self-diagnosis. make sure code no.43is not displayed. make sure that throttle sensor is not in"fail-safe" state.4.disconnect throttle sensor harness connector5. if idle speed drops, INSPECTION ENDS.6.if idle speed does NOT drop, GO TO B. B.Check Power Supply 1. stop engine2. disconnect aac valve subharness connector3.turn ignition switch to "ON"4.check voltage between terminal "e" and ground.5. battery voltage, go to 'C"6. if not battery voltage, check harness connectors, 10a fuse, harnesscontinuity between aac valve sub-harnesss connecot and fuse C. Check output signal circuit1.turn ignition switch "OFF"2. disconnect ecu harness connector3. check harness continuity between ecu terminal 113 and terminal "f"4. continuity should exist

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General trouble-shooting guide. Not especially helpful in my experience.

TROUBLE SHOOTING (1991 240sx)******************HIGH IDLE: 5,8,13,21 UNSTABLE IDLE: after warm-up:-10,25,2,4,7,1,13,8,3,12,17,18hunting:-13,25,7,8,10 ENGINE STALL: Cold-9,25,2,4,7,1,17,19,18Hot-15,25,,2,4,1,17,19,18,20On momentary acceleration-9,25,2,4,1,17,19,18after deceleration-9,3,25,2,4,1,13,17,19,18acceleration or cruising-25,2,4,1,8,17,19,18heavy electrical load-6,25,2,4,1,17,19,18While turning-25,2,4,1,17,19,18

Symptom definitions:===============1.ensure fuel pressure within spec2.perform appropriate test in injector malfunction diagnostic chart3.inspect throttle body ports and valves for deposits, wear or plugging4.check for spark using spark tester5.Check idle speed control circuit. 6.Ensure battery is fully charged and maintains at least 9.6 volts during cranking.7.check spark plug gap and fouling8. ensure no vacuum leaks in intake system9.Check fast idle system.10.check egr control valve operation11.Check EGR control valve solenoid operaton.12. check engine compression13. disconnect exhaust gas sensor and monitor change in driveability. if it improves, replace sensor. if not, go to 16.14.Remove canister purge line from intake and test drive vehicle.15.Remove vacuum hose from fuel pressure regulator and monitor for symptom change.16.enter self-diagnosis mode 11 and monitor exhaust gas sensor operation17.check ecu harness connector18.try a good known ecu19.Check ECU power source and ground circuit.20.Check timing belt for proper installation(V6 models)21.Check throttle linkage operation.22.Try a known good airflow meter.23.Check for intake valve deposits.24.Check engine temperature sensor25.perform power balance test

Related Links

http://zilvia.net/f/tech-talk/...79043

Intake manifold SOHC

Modified by vancouverbc at 3:02 PM 10/19/2008

Modified by vancouverbc at 3:03 PM 10/19/2008

Modified by vancouverbc at 1:14 AM 2/10/2009
Modified by vancouverbc at 9:01 PM 3/25/2009

I would say that it is definitely not easy to remove the iacv by any means. I don't know what tool you used to get the bolts off but i used a tiny ratchet which seems the only thing to use because the space is so tiny to move around and that's even not that easy. And removing the connectors and hose going into the valve is definitely not very easy especially if it hasn't been touched in say....14 years. Putting the unit back on is just a little bit harder then taking it off also. If you have baby hands then yes this might be a bit easier to accomplish. Overall though, good write up. I took mine off to clean it because my car was stalling when I would decelerate ( rpm's would drop below 500 and pop back up but sometimes stall). There was a lot of build up but a full can of carb cleaner took car of that. Haven't driven around yet but will post again with results soon.
Modified by donasmello at 11:27 AM 5/24/2007

mother****ing awesome!!!! I was just about to improvise and attempt this. Now at least I have some guidance. Step by step instructions FTW.

This NEEDS to be sticky!!

hi have you fixed your stalling problem yet? I think the same thing is happening to mycar and i cant sort it out...

whats it mean when you say throttle sensor in "fail-safe" state? I have a high idle problem but when I position the TPS closer to the full clockwise position, my idle drops to where it should be... same effect if I disconnect the TPS harness. Thats the only way I can get it to idle, but theres a noticable change in accelleration (more sluggish).

Appreciate your concerns, but this is a tutorial for cleaning iacv. Criticisms and suggestions for improving tutorial are welcome.

Ghetto way to clean iavc is.

step 1. start carstep 2. while having a friend rev engine, partially remove the 2ND (bigger of the 2 hoses) right beside eachother on your intake(stock - going from engine to airbox) step 3. if you have managed to keep car running while pulling it PARTIALLY OFF then continue if not restartstep 4. spray a **** load of throttle body cleaner in there and reatach hose while keeping engine running. repeat as needed

still like ur method though but it takes tools ol lady took mine but hey no better reason then to go buy more

You THE man Van BC!

I took out my AAIV a while back and just cleaned it out with

Carb Cleaner and never tested it, Most of the time, the thing is just clogged up.

Great write up.

skatermatt180 wrote:This NEEDS to be sticky!!

It is a sticky. Just check the tutorials sticky on the NOM front page.

duh lol

Is there a gasket or washer between the unit and the manifold???

S3t0_S13 wrote:Is there a gasket or washer between the unit and the manifold???

not on mine.

SWEET, maybe this will fix my fluctuating idle.

CrypticScorpio wrote:Ghetto way to clean iavc is.

step 1. start carstep 2. while having a friend rev engine, partially remove the 2ND (bigger of the 2 hoses) right beside eachother on your intake(stock - going from engine to airbox) step 3. if you have managed to keep car running while pulling it PARTIALLY OFF then continue if not restartstep 4. spray a **** load of throttle body cleaner in there and reatach hose while keeping engine running. repeat as needed

still like ur method though but it takes tools ol lady took mine but hey no better reason then to go buy more

anyone have a pic of the intake tube ("ghetto way") to cleaning the iacv for an sohc motor? if not even a pic of the dohc would be great... i just dont want to take apart the whole iacv since its such a ***** to take off..

Not ghetto at all. This is the way I do it. Doing this every couple of months prevents it from becomming clogged. If it's already clogged then you'd have to remove it.

240FeVeR wrote:Not ghetto at all. This is the way I do it. Doing this every couple of months prevents it from becomming clogged. If it's already clogged then you'd have to remove it.

Doing it every couple of months seems excessive. I cleaned mine after 14 years and it wasn't all that dirty. Maybe you have a bad PCV valve or something?

on the sr there is a paper gasket.

I just took mine off and cleaned today. man what a pita. luckily my buddy helped w/ his small *** hands. I think it would be way faster to just pull the mani off.

aziankingz wrote:anyone have a pic of the intake tube ("ghetto way") to cleaning the iacv for an sohc motor? if not even a pic of the dohc would be great... i just dont want to take apart the whole iacv since its such a ***** to take off..

Interested in this as well. I can't find many pictures of the location of the KA24E IACV.

Also, does a clogged IACV result in bad cold start idle?

a air regulator that doesnt open when car cold would cause a problem with starting when cold. see air regulator in tutorials

Air Regulator Tutorial Link is busted. It takes me back to Nissan Online Mechanic Subforum, not directly to a thread/post. I'll search, but that might need fixed.

PHeller wrote:Air Regulator Tutorial Link is busted. It takes me back to Nissan Online Mechanic Subforum, not directly to a thread/post. I'll search, but that might need fixed.

thanks.

zerothread?id=378625

you can google 240sx tutorial and what your part is and it usually comes up as top result in google

vancouverbc wrote:

Im assuming that air regulator needs to stay there for cold starts and the back IACV can be removed....

both are essential. you'd be very miserable w/o them.

vancouverbc wrote:both are essential. you'd be very miserable w/o them.

hmm thats odd cause i hear stories on-line from a few people that have removed them and they have no issues... But i have yet to personally speak with one of them to see if these rumors were true..I guess i can just remove them and spray them down real good with carb / brake parts cleaner.... Hopefully it will cure my rough cold starts and extemely lean idle conditions...

heres an old article on sohc air intake showing location of iacv for sohc

Intake manifold SOHC

i am trying to take the iacv valve in order to clean it and hopefully solve my fluctuating idle problem. i have managed to take out the 4 bolts fairly easily but having trouble with the hoses being held by the metal staples.

anyone have any ideas or suggestions on taking the hose off?

jngai wrote:i am trying to take the iacv valve in order to clean it and hopefully solve my fluctuating idle problem. i have managed to take out the 4 bolts fairly easily but having trouble with the hoses being held by the metal staples.

anyone have any ideas or suggestions on taking the hose off?

needle nose pliers for hose clamp. same with the staples holding the plugs. find another plug with staple to practice on.

anybody else order a new iacv and find that the plugs are incompatible with their harness.

hey guys my car seems to be in need of an IACV AAC cleaning but i'm not sure. So the problem w/my car is that it will randomly idle outta whack or when I am driving it hesitates badly and blows a lot of black smoke. Weird thing is that once in a while it will do it, other times my car runs great. So my question is, if my IACV AAC were clogged would this problem i'm having be more of a constant/continuous problem or can it come and go as i've explained? Again my car will run good then all of a sudden like someone flipped a switch my car bounces between 200-700 rpm and it feels like it will die if I don't keep on the gas. Think its IACV AAC? I've followed the tutorial on here for how to clean the PAIR valve but what do you guys think?