iacv-aac cleaned / still idle high / hunting...

[vancouverbc]

Brilliant! This thread is going to help alot of people. Thank you for sharing:)

[vancouverbc]

I took my IAA unit out of the car tonight too.(surprised how easy it was).At first , I though my aac solenoid was defective because when i applied voltage there was no noise and piston did not move. The piston just stuck out a few milimeters(with or without power applied. I then realized that piston becomes stiffer when 12 volts applied but no noise. I also noticed that aac valve does not close fully when power is not applied. So, my piston is always sticking out . it never retracts. it does firm up when power is applied. It appears I have the same problem as you. The spring that shuts aac valve is too weak to close valve fully.

my main problem is that car stalls when decelerating to stop. does anyone know what the iaa unit does when car is decelerating to keep idle right?

fsm says the following: "a vacuum control valve is also installed in the IAA unit to prevent abnormal rise in intake manifold vacuum pressure during deceleration"

anyone know which valve this is? what does rise in intake manifold vacuum pressure mean? vacuum gets deeper or you lose vacuum?

Upon closer scrutiny, i see that aav valve is open about an 1/8 inch . there was so much buildup of gunk i though it was part of plunger. Now i have to try to get the big brass screw out. looks like a weak spring is the main problem.

Modified by vancouverbc at 1:16 AM 7/13/2005
Modified by vancouverbc at 1:26 AM 7/13/2005

[kirk]

It does sound like your spring is weak. I never tested my solenoid. When I removed my solenoid, the actuator was sticking out, but I could push it into the body of the solenoid freely, and it would come right back out.You might try compressing the spring by pushing the plunger all the way into the body, and then spraying some B-12 on it. Maybe your spring is good, but your plunger might have too much goo on it to seat properly.But you should be able to tell pretty easily if your spring is weak. I could actually hold the IACV in my hand and shake it, and you could hear the plunger would move around!!!!

Removing the epoxy was a pain. Just get a small sharp chisel, and put the IACV in a vise. Take your time. You should be able to see the brass easily when you get to it. You will also need some sort of sharp pick to get the epoxy out of the screw slot on the brass plug. Also, try and remove as much epoxy from the threads as possible, so the brass plug won't bind up. BE CAREFUL when removing the brass. You can ruin it VERY EASILY!!!!!! It is a lefty-loosy.

Abnormal rise in intake vacuum means that whenever you have your throttle plate open (as when driving) and let completely off of the throttle without the car in a gear, the rapid shutting of the throttle plate will cause a high spike in vacuum (more vacuum). I think that's how it works.

I am under the impression that the IACV-AAC will activate during this situation, and allowing air into the manifold past the throttle body, "raising" the idle, causing it not to stall out. I could be COMPLETELY wrong there. Just a thought!I don't believe there is a "vaccum control valve installed in the IAA unit". If there is, I didn't see it!

As a side note, my Air Regulator IS bad. Got in my car this morning to come to work and I had to keep it running for a while with my foot.Now I've got THAT to worry about!!!!!

[vancouverbc]

"When I removed my solenoid, the actuator was sticking out, but I could push it into the body of the solenoid freely, and it would come right back out."

Same with me. FSM never mentions checking aav solenoid for noise so i don't think it makes noise. They do mention checking ficd solenoid for noise.

Yep, my spring is weak. Now that gunk is gone, there is at least an 1/8 gap between spring and piston end. ie spring is too short to close valve. I am thinking that aav valve is controlled by vacuum to some extent. when vacuum goes deep when decelerating , it opens to let more air in. not sure how tight spring should be. OTOH, they may mean that ecu monitors vacuum and opens aav valve when it senses vacuum go deeper upon deceleration.

thanks for the lefty-loosy tip!

i think i have multiple problems too. i used to have a stable idle of 700 before i cleaned throttle and ground and removed aiv. now my idle is high.

good luck with air reg valve:)

[kirk]

It's funny you mention the high idle after cleaning your throttle body, because that is exactly what happened to me. In hopes of clearing up my stumbling problem, I had cleaned my throttle body (it was really dirty), and put everything back together, and the idle was a lot higher....Maybe the better seal around the clean throttle body increased vacuum causing the plunger in the IACV to stay sucked in the whole time..... (kind of a stretch)

It's a VERY interesting idea about the spring controlling the amount of vacuum let into the manifold on decel. That just might be what the FSM is referring to when they say "vaccum control valve installed in the IAA unit".... I guess I could try and tighten my spring with the brass plug and see if my car dies on decel...... It would be interesting to see.

Let me know if you need more info on the shim I used. I can probably get a pic if you need it.

I don't know if the ECU monitors vacuum or not. I think it would have to, just so it could send a signal to the AAC. But maybe it sends a signal to the AAC based on other factors.

Keep me posted!

p.s. Started the car for lunch and had to keep it running for a while with my foot. It definately want's to idle where I set it! It's kind of cool though. Reminds me of the days driving old beat up carbureted cars.

[vancouverbc]

Try loosening your aav screw because aav may not be able to open up enough when starting in cold because your rubber shim is not compressable. I'm assuming ecu tries to open aav wide open for cold starting.

I put my cleaned iaa unit back in today. My idle is stable now when i decelerate to a stop. It used to drop 300-400 or more rpm and stall. My idle is still high at 900 so I need to work on that a bit.
Modified by vancouverbc at 9:22 PM 7/13/2005

[vancouverbc]

This might be relevant. I cleaned my throttle some more and adjusted the calibration screw( not supposed to do this) so throttle closes more during idle. My throttle is not binding so i think it is ok. Anyway, after I did this, my car would immediately stall when I tried to start it. I had to rev it a couple times before it would maintain stable idle. Raising the idle did not seem to help. I opened one vacuum tube that used to go to iav and the car ran perfectly. I then blocked it off again and backed off the aav screw and now my car is running perfect a 725 rpm idle. I think I will take rubber shim out of aav and see how that goes. My idle is 1000 when I first start car. My vacuum is 26 inches of mercury stable.

[nyckanny]

how did you guys clean the iaa unit, did you just disassemble everything and soak it? I have not taken the unit out yet, so i am not sure what parts require cleaning.thanks

[vancouverbc]

I just sprayed some carb cleaner on and washed it off with cloth. I also used q-tip . the only part i really needed to clean was plastic piston that closed aav valve. it is easy to clean.

[InsanityInc]

Your knock sensor is most likely bad. Almost every 240 has a bad one, and it makes your car much slower under heavy throttle as detecting a fake knock makes the ECU d!ck with your timing.

[zero_gripS13]

ok gvuys u seem to be on a roll with dile problems... well heres mine.. ..and its only done it after i converted to 5spd...but anyways..

car idles around 800 +/- ..it doesnt idle low it doesnt idlke high, its just about rihgt...BUt when i rev it or and going down the road an put it in neutral it decelerate but once the rpoms get to around 1500 it stays there for like 10 secs+ then drops back to normal idle...well tonight i removed the itnake, cleaned the throttle body up (kinda grimmy in there) and checked to see if my maf was dirty (that thing wa sreally clean).. and cleaned up my air filter ... but othing helps.. my car seems to have better throttle responce and delerate better now that i cleaned it, but my idle still doesn the sma ething... is there a vacuum line on the back of the motor that i might of unhook when doing my 5spd swap??

thansk in advance

[AR31TU]

As a side note, my Air Regulator IS bad. Got in my car this morning to come to work and I had to keep it running for a while with my foot.Now I've got THAT to worry about!!!!!

So the IACV really crapped out this time? :O

[tramp_drift240]

what am i supposed to clean if my iacv unit doesnt have a spring or plunger?

ive got high idle and im not sure what's goin on, so i took mine off to investigate. but now im more confused than before, since i dont have a plunger/spring inside.

[ioioioio]

Hmm.. I guess everyone has their own probs.. Tried this and it didnt work for me,.. but it could work for someone else. I might have done something wrong tho..

Kirk - what was the length of vacuum hose you used to put into the brass plug? did it sit flushwith the top of the nut?

FIXED!!!!!!!!!!!!!!!!

A big thanks to everyone who has posted back to me on this topic!!!!! I couldn't have done it without you guys!!!!!!!! YOU RULE!!

Got home. Let the car cool down a bit. Pulled plug off of AAC. Car idled the same. Hmmmmm.....So I went ahead and pulled the codes on the ECU:

12 - MAFI figured it would throw this because I had unplugged my MAF while it was running.

13 - Engine coolant temp sensorSame thing, pulled when the engine was running. (man that computer is GOOD!)

34 - Knock Sensor CircuitHmmm... come back to that later

45 - Injector leakWhat the heck?!?!!?! OH well.

So I reset the codes while I was in there. And it showed 55. YAY!

Here was my train of thought.1. Air regulator can be ruled out. Car idles high when cold, and idle goes down after warm.

2. FICD is good. When I activate A/C, idle goes up.

3. That leaves me with the ACC. Since I unplugged it and the car's behavior didn't change one bit.

Took IACV-AAC off of car. Tested solenoid again. Read 10.7 ohms. So solenoid is "good"Got to looking at the AICV unit itself and LOW AND BEHOLD THE SPRING WASN'T DOING IT'S JOB!!! The spring had gotten weak over time (I guess) and wasn't pushing the plunger against it's seat!!!! YAY!!! Now how do I fix it? I'm only going to buy a new one as a last resort!

If you ever notice on the same side as the idle adjust screw, there is what looks like an epoxied hole. Well, if you chisel away that epoxy (jb-weld) stuff, there is a Brass screw that holds in the spring and plunger. (see attached pic)http://nissaninfiniticlub.net/...t=500

I thought about how to get another spring that was the same, but then I realized it would be a whole lot simpler to just shim the spring. So I cut one of my vacuum hose plugs (like a cross-section) and this fit PERFECTLY into the brass plug. As you can see in this next pick, the brass plug has a seat for the spring to rest in, and the donut shaped piece of rubber fit just perfect. I couldn't have planned it better myself.http://nissaninfiniticlub.net/...t=500

Put it all back together. Now I have adjustment with the brass plug on how much seat pressure the spring will apply to the plunger. I thought that might come in handy in case the solenoid isn't that powerful.Anyway, put it back on, car ran just DANDY and now I can adjust the idle down to 600 (with tps unplugged). I actually had to idle it up a little, because I'm so used to it running so high!!!So my brother and I went out for a ride, and the car runs just PERFECT!!!! Idle goes right down when getting out of gear. Idles like a stone! Just completely fixed my problems!!!!

Sorry for the long post, I'm still so excited!!! Just had to share with you guys. Thanks again for the help!!!! I wish I could shake your hand and tell you how much I appreciate it!THANKS!

p.s. pulled the codes when I got back and still had the 34-knock sensor, but I'll save that for another topic and another day!

THIS FORUM RULES!

Modified by ioioioio at 5:57 AM 4/20/2009