IACV (Idle Air Control Valve) Test

[REI600]

So, as stated in some detail in my introduction, i have been having some issues with my Leggy. I have been running into dramas when i've been starting her up, usually when cooler, and she has dropped all ignition and died. Some F'ing awesome chap on here gave me a hint to check the IAC as it is a known issue with the engine and it is something that i hadn't been told/shown up until that point.

I did a bit of searching and found a video on YouTube that showed me one way testing the IAC and also how to clean it up.

I'll say that this is not a solution for me, more of a crutch. I will be looking to get a new IAC just as soon as i can get my fuzzy little hands on one.

So, as in the video, gained access to the IAC and unbolted it from the throttle and sat it safe and sound. I had my lovely assistant (my wife) video taping the process so i could see and, if you guys weren't 100%, maybe show you guys something too.

As you'll see in the below photos and video, it IAC is filthy and really needed a good cleaning. It was recommended that i use a toothbrush and clean the residue off with a clean rag.

First video :

In this - on the third or so time i turned the key, the little IAC was trembling with fear (or for some reason unknown to me). I think that is a pretty fair sign it is not working as the factory intended. You can also see how filthy it is. The photos illustrate that a lot more clearly though.

Second video :

This is after i cleaned it and wiped it all down. I dont think it is perfect now but, as you can see, it is a lot less shaky than in the first. I can only assume that that is a good thing. After this video was taken, i strapped it all back together and did everything up nice and tight and started her up to make sure i didnt fry anything.

She turned on. I was thrilled.

After that, i came back around and lightly played with the throttle as that was what was causing the issue all the other times. I did it a few times so i will know a little later how well i've done but... hopefully it'll last until i get my mitts on a new one and fit that.

I dont know if this was of any use to you guys or news to anyone but i was having dramas and something like this may have helped me out.

So, to Access the IAC, i just removed the intake run basically, the bonnet "scoop", the air box and the pipe leading directly into the throttle. All this was simply to create enough room to see and play more than anything else. The bolts on the IAC are little 8mm bolts with philips head centre, i used a spanner to just break the tension and the bolt cam out great. The rest is REALLY straight forward. I've thrown a photo up to help locate the little beastie it could have been in a worse spot...

The test is to simply have it setup up the way i have here, have it plugged in, and turn the key on to accessories and off again. repeat this and this little solenoid should so as this one is doing... hopefully with less shaking turn it on for a few seconds, then off and repeat.

DO NOT CRANK THE ENGINE!!!

(not my picture. Just a GREAT one.)

IAC is the lower, right hand highlighted circle.

Hope this helps someone That'd be cool.

Thanks for the help up to this point guys it was awesome and invaluable

 

[Guest]

ISC issues can also be TPS related as there is idle switch in there that activates it when there's no throttle input. The best way to diagnose all this is using Evoscan, but you can adjust the TPS idle switch for correct operation using a multimeter.

See these threads for more info...

http://www.ozvr4.com/threads/isc-idle-stepper-servo-diagnosing.12177/

http://www.ozvr4.com/threads/test-tps-sensor.12285/#post-260583

 

[REI600]

I Have the multi there and can check that out this arvo. I am not sure at all what evo scan is...

I'll look into it as it sounds like it'd help things along a bit.

 

[REI600]

So, on the recommendation of a few folk on here, i invested in a shiny MultiMeter and did a little digging around under my bonnet this evening... Turns out... my vehicle has more and more character the more i look... which isnt to say i am growing more and more fond of her... To the point where i am hesitant to name her yet.

Results:

top to bottom = left to right. (top = constant)

Multi set to V (DC/AC Auto -- jaycar multi meter).

I read the post about testing but something about that made no sense to me at all... So this is what i got on the 4 pins that are there.

More interestingly though... something even stranger happened and i took a little video.. for give quality and lighting and the lack of dialogue... hopefully you guys have run into this before.

This:

I was testing the plugs and had stepped back to write down some results and then it started doing this... Seems to be coming from the IAC and if youy've watch the previous video... the shaking that it was doing in that, could be happening again in this. Also, it was warming up... the car was not turned on (idling) as stated earlier.

What do you guys make of this???

 

[Dice]

That happens to mine when left on idle for too long. I've seen other members cars to that too I assume it's normal.

Edit: Not idle, I meant ignition on but engine not running.

 

[BCX]

That happens to mine when left on idle for too long. I've seen other members cars to that too I assume it's normal.

Edit: Not idle, I meant ignition on but engine not running.

Correct, this is normal and documented in the factory manual of most Mitsubishis

 

[BCX]

Results:
top to bottom = left to right. (top = constant)

View attachment 25345

These voltages don't seem right.. 49volts? Your meter might be auto ranging to mV (millivolts)

The TPS works as a potentiometer. One pin should have 5v, one should be ground and one will be the potential between to two (ie between 0-5v). At throttle closed, you want to set it to 13.3% or 0.665 volts.

Last pin is the throttle closed switch.

Multi set to V (DC/AC Auto -- jaycar multi meter).

Wouldn't surprise me if they Jaycar meter is the reason you're getting inaccurate/erratic readings. I had a cheap meter for a while, then just forked out >$150 for a nice Agilent meter. Best thing I ever did.

 

[VOLK]

ISCV slight shake upon initial ignition normal. Noise above normal too.

Testing TPS is done with Ohms, not DC. http://www.ozvr4.com/threads/test-tps-sensor.12285/#post-260583

 

[BCX]

Going back to your original problem about misfire at idle when cold...

Have you checked:

• Ignition coils, leads for any signs of earthing?
• Check each spark plug, ensure they are all consistent colour?
• any other symptoms? black smoke from exhaust (ie running rich when cold)
• vacuum leaks/boost leaks?

 

[REI600]

BCX -- maybe i said it wrong - idle is great, cold or warm. idle is not the issue. The issue is when slight/steady throttle is applied -- car cuts ignition.
As for the tests - leaks etc, yet to be done as i dont have an air compressor and i cant get the car to where there is one. As for spark plugs - actually a great idea although with how it is running at the moment, safe to say these will all be pretty crappy and black. The issue i am having will give a false positive RE: spark plugs. As for the test on the Idle Speed Control -- Thats another one i can do tomorrow should i have enough light.

VOLK -- So - "top" is set at a steady 5v, the others i check with ohms. Easy enough. Will do it tomorrow. As for the shake to be normal upon initial start up... that video was recorded quite some time into me testing. As Dice mentioned.. apparently thats a normal sound for these cars...

As for the little jaycar warrior - ive not given up hope on them it wasnt the cheap nasty one by any means. We'll see how it goes for now I just took another look at it and figured out how to stop it ranging to mV. I'll have another crack at it in the arvo The TPS and ICV are going to get attacked

Thanks guys

I am a newbie when it comes to car electrics so, i appreciate the help and the patience

 

[VOLK]

Sorry, my post must've been to brief. What I meant: the initial slight shake/tremble is normal that you reported in your first post AND the chatter comes during extended ignition on, not running, is also normal. They don't go through a step cycle like GTOs when you first turn the ignition on.

Even though it sound like the solenoid is working fine, here's the test method http://www.stealth316.com/2-isc-iac.htm

 

[REI600]

VOLK - I figured it wont hurt to replace the stepper motor so I've organized one of them. My main testing is going to be with the TPS at this stage.

I will head home this arvo and crack open the Leggy again and have another go at testing it. This time at least, the "top" point is constant so I know that much. I will just be testing the remaining points using Ohms. I will read about what to test the resistance against (which points against which points etc) and I SHOULD end up with a result that makes a little bit more sense.

 

[REI600]

Sooooo..... on the subject of how to treat the TPS. How does one physically do it?

I know the equipment i need and what should happen when i do test but.... how to i go about actually testing it?

Back probing is a common method but I'll be buggered if i know how to get that done on my sensor connection without damaging it.

Has someone got a method or video or step by step deal on how to get this done?

Did the ohm test tonight. Point 2 reads 0.663 m ohm. Point 4 reads at 0.415 k ohm.

I think it is where it needs to be when shut.

 

[REI600]

So... i looked a little more into back probing so... this is the result i got. It makes no sense to me at all... hopefully someone on here knows what is going on.

Probe locations: RED - pin 3 and BLACK - pin 2. =

This test, as you will see, as i am opening the throttle, the volts are decreasing... until the throttle is wide open where it reads 0.11v... My assumption is that i had the leads the wrong way around but i checked and that's how i've been told to do it (red signal, black "earths")

Probe location: RED - pin 3 and BLACK - pin 4 =

This one though just jumped to 4.84v and stayed there... no real progression at all.

I also decided to test the Volts on the IAC. I know it does really tell me a thing but... i forgot which probes go where when testing resistance. That and it mentions the special test harness...?? I have a multimeter... will that suffice?

 

[REI600]

so yeah... maybe what i am dealing with is so unique that no one on here has a clue what's going on...

Pretty stuck at the moment... know idea whats going on with this bloody car.

Hoped someone on here would be able to shed some light but... maybe not.

 

[REI600]

has no one on here ever had this issue or know about this issue?

No one has some tips for me at all??

Sucks... A Lot!!

 

[VOLK]

Yes mate, I've had similar issues, I posted links to the threads in which I diagnose and fix.

My fault was caused by wrong TPS idle value.

 

[REI600]

Yes mate, I've had similar issues, I posted links to the threads in which I diagnose and fix.

My fault was caused by wrong TPS idle value.

In that thread, you said something like this - "Still measuring pins 2 and 4, open the throttle slowly and observe the dc voltage should increase to a max of 5 volts at wide open throttle."

Way I have always been shown, seen and told is that the voltage on both 2 and 4 should increase gradually as the throttle opens. The videos I posted show that this is certainly not happening with mine. In fact, pin 2 is decreasing in voltage is it opens and pin 4 is spiking to 4.84v very early in the throttle position and staying there.

You also mentioned - "volts between pins 2 and 4 should be in the range of 400mv to 1000mv". I did this test with the earth lead on the earth and the + lead testing the pins 2 and 4. Is that the correct procedure to find the voltage of these two pins?

I have looked on here all over but there is no real assistance in regards to "walkthrough" for newbies and multimeters... tried to read what I could and watch what I could and hope for the best.

If there is something that I have obviously done wrong, please, I'd LOVE to be corrected.... I wanna fix this damn car!!

 

[REI600]

The above is what is happening to me. I haven't read anywhere that a decreasing voltage for the TPS is normal. Nor has anyone been able to let me know what the issue MIGHT be...

This is the instruction guide that I have found and is pretty typical of what is around. It states as well that a good range is .45-.48v closed and 4.5-4.8v open.

yeah... nah. not what I am getting... at all... Are the legnums meant to go down in voltage the more the throttle is opened? and raise in voltage the more you close it?

 

[BCX]

I'll check my TPS tonight and let you know which pins you need to be probing. If you are going from 5v -> 0v as your throttle increases, sounds like you're probing the wrong pins.

Try probing the pin you think is the 'signal' pin and earth (body, engine, - battery terminal, etc). You should see voltage increase as throttle opens (ignition needs to be on of course, and ensure your meter probes are in the correct hole for measuring voltage, otherwise you're going to have a bad day)