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1) is a evo 9 IAC different than a 8? Does the 9 have the spring exposed while the 8 doesn't?
2) will IAC's from other 4g63 Mitsubishi's (like a 2G dsm) work in a evo 8/9?
3) In the photo below. Left is what was in my evo 8 and was not idling well. Right is what i put in and fixed my issue. Is the one on the left simply designed differn't, or it is a way to detect a worn out IAC?
I believe you're correct that the 9 has the exposed spring while the 8 doesn't (has the rubber piece)
Other IACV will fit, it's a mopar part so a lot of Chrysler will fit also.
That said I went through 3 in 6 months on my 9 before I bought OEM. Didn't have a single issue after that. You can pull the ECU fuse to reset and test the IACV. There are a few procedures on EvoM and videos on YouTube also for how it should act when you first turn key to 'On' position
On the Evo 8 IACV, the four raised ridges around the circumference of the inner plunger barrel get worn down, and the slots in the outer barrel get worn. You can see this on the one you replaced. This eventually allows the inner plunger to spin at the higher extensions, so it no longer moves in and out and cannot control idle. The answer is to use the one off the Evo 9 with the external spring. This is a better design and does not suffer from the worn ridges problem.
On the Evo 8 IACV, the four raised ridges around the circumference of the inner plunger barrel get worn down, and the slots in the outer barrel get worn. You can see this on the one you replaced. This eventually allows the inner plunger to spin at the higher extensions, so it no longer moves in and out and cannot control idle.
That was my guess. I just never saw it documented anywhere before. It is good to know there is a way to visibly tell its getting worn out.
Originally Posted by cdrinkh2o
The answer is to use the one off the Evo 9 with the external spring. This is a better design and does not suffer from the worn ridges problem.
Have you done this? Can you verify the 9 IAC will work correctly in a evo 8?
That said I went through 3 in 6 months on my 9 before I bought OEM. Didn't have a single issue after that.
I've heard similar stories. Hopefully if a worn out one is visible like mine is, it can help people possibly know a "good" used one when photographed properly. Do you happen to have any of your old ones that didn't work that you could still look at?
Originally Posted by llDemonll
You can pull the ECU fuse to reset and test the IACV. There are a few procedures on EvoM and videos on YouTube also for how it should act when you first turn key to 'On' position
I did the key cycle re-set procedure i read on here(evoM) when i swapped them. I don't think it really did anything.
My car is a 2003 and I replaced the radiator, a radiator that never leaked. Same story with the front wheel bearings. I was just looking for possible failure parts. The only things that have failed on my car are one tie rod end and one front strut. This with 16 years of service. So, I think the story here is, for the IAC,, like other parts, is that Mitsubishi used the best stuff available - there's apparently various grades of parts. How else can we explain this reliability? So, spend your money and go OEM.
My car is a 2003 and I replaced the radiator, a radiator that never leaked. Same story with the front wheel bearings. I was just looking for possible failure parts. The only things that have failed on my car are one tie rod end and one front strut. This with 16 years of service. So, I think the story here is, for the IAC,, like other parts, is that Mitsubishi used the best stuff available - there's apparently various grades of parts. How else can we explain this reliability? So, spend your money and go OEM.
I'm not debating OEM is best, i'm just trying to know my options.
My main hope in this thread is:
1) being able to know for sure your current IAC is bad before spending the money on new one.
2) being able to tell if a used IAC is good (or, for sure know the used one you are looking at is bad!)
3) If your going to buy a new OEM and a OEM 9 IAC is a better design than the OEM 8 as stated, wouldn't you buy the OEM 9 if it works on your 8?
1) is a evo 9 IAC different than a 8? Does the 9 have the spring exposed while the 8 doesn't?
The only wrinkle I know of in addition to the posts here by other members is that the 03/04 throttle body is a different part than the 05/06.
The IAC design seems to have changed at the same time as the throttle body.
I have a 05 Evo8, and the IAC has the external spring design.
I checked in the 03 and 05 service manual for any tolerance specs on the IAC, and the only thing I see are checks to test if the motor is bad (checks resistance and actuation).
There is nothing in there to determine if the IAC plunger is simply worn out
The early 2000’s Mitsubishi Galant will interchange as well, I usually grab 1 or 2 when I’m at the junk yard to have spares. That’s good to know on the worn down ridges.
I am on speed density and in the winter, the engine will turn over without issue, but after half a minute, the rpm will rise slightly, drop, and then stall unless I blip the gas to keep it going. Once warm, it idles on it's own without issue until I coast to stops. Like the video posted by BoostedFilms, my idle bounces around several times before settling after a few seconds. A/C on, the car sometimes dies clutch in-coasting to a stop. Car drives and boosts fine otherwise, and tuner did not find any issues.
My IAC appears to be the non-Evo version, MD628117 for the eclipse/galant/etc based on the housing shape. It passed the startup self-check test and resistance is 30 ohms between the pins. For whatever reason, the person who sold me the car swapped a '03/'04 TB onto my '06, it has the warm up flap part. I wanted some opinions on the best course of action...
1) Keep the '03/'04 TB (check/replace seals as necessary) and buy the OEM Evo 9 IAC and hope that it fixes the idle problem? Or..
2) Replace current TB with the '05/'06 that the car should have came with. From what I researched, they are interchangeable and the function of that warm up flap is insignificant. However, I want to avoid any possible variables that prevent me from solving the issue.
I am on speed density and in the winter, the engine will turn over without issue, but after half a minute, the rpm will rise slightly, drop, and then stall unless I blip the gas to keep it going. Once warm, it idles on it's own without issue until I coast to stops. Like the video posted by BoostedFilms, my idle bounces around several times before settling after a few seconds. A/C on, the car sometimes dies clutch in-coasting to a stop. Car drives and boosts fine otherwise, and tuner did not find any issues.
My IAC appears to be the non-Evo version, MD628117 for the eclipse/galant/etc based on the housing shape. It passed the startup self-check test and resistance is 30 ohms between the pins. For whatever reason, the person who sold me the car swapped a '03/'04 TB onto my '06, it has the warm up flap part. I wanted some opinions on the best course of action...
1) Keep the '03/'04 TB (check/replace seals as necessary) and buy the OEM Evo 9 IAC and hope that it fixes the idle problem? Or..
2) Replace current TB with the '05/'06 that the car should have came with. From what I researched, they are interchangeable and the function of that warm up flap is insignificant. However, I want to avoid any possible variables that prevent me from solving the issue.
Any suggestions are appreciated, thank you!
The problem that comes to mind on this setup is a mismatch between the ECU and the throttle body hardware. The ECU on a 05 and 06 will assume that the flap is absent and will not expect the extra air. This could explain why you have idling issues only after the car is warm. If it were my car, I would get the proper matching throttle body part. But, sealing off the flapper intake area in some way so that it operates just like the 05/06 part should work as well.
I'd be dubious of the length of the IAC plunger too, if its not an Evo part. The ECU will command it to a certain step height but that height may not match the Evo part. I'm not sure what the cheapest route for you would be because both the IAC and throttle body are expensive parts :|
Last edited by carbon_toast; Mar 6, 2020 at 10:52 AM.
Reason: IAC
I'm in the middle of swapping mt IAC; my idle issue shows up when driving 45-60 min in traffic, and suddenly my 03 VIII won't idle. Take my foot off the gas and clutch in, and it stalls in about one second. Otherwise it drives normally. I'm hoping that the actuator motor thing is bonking out at high temps and holding that little plunger in and not letting any air in. It's slowly getting worse. I have an aftermarket IAC from Amazon to place in, and if my problem goes away I guess I'll consider getting the Mitsu version long term.
