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Thread: EJ20G How to Remove IACV to clean it to cure cold start stall problems and wild idle

  1. #1

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    Default EJ20G How to Remove IACV to clean it to cure cold start stall problems and wild idle

    A dirty or defective IACV (Idle Air Control Valve) can be the cause of a few issues for WRX owners of any year or Impreza in general.

    Common Symptoms:
    • Car stalls immediately when turned on when cold (especially on EJ20G) (this is also known to be caused by the temperature sensor-thx to puckhead for this)
    • Car idles too high or fluctuates or maybe even stalls in traffic (often IACV but can be MAF too)
    • Car cannot hit boost (could be boost leak or other issues, but IACV can cause this)

    Remove the IACV and clean it out good with something like brake clean or carbon cleaner (although I heard carbon cleaner may eat away at the rubber lining and it may not be recommended).

    *Update it is debatable if the IACV is really the true cause of cold start issues. I replaced mine with a brand new unit and it didn't make a difference. There is one member here who says it did cure it. Another member said they had the same issues as most of us and found 2 of their injectors were/dirty/bad clogged and replaced the two bad injectors.

    *Update 2010-11-03 a member albertfalgui had his mechanic grease his wiring/sensors and this fixed the issue. It's not clear how/where this grease was applied but the thread is here:

    One person reported that changing the coolant temperature sensor fixed their problem (I have replaced it and it did not help).


    The biggest concern I've heard is that this issue could cause the car to run lean which is very dangerous and potentially could mean a quick and early death for the engine.

    I want to remove mine on EJ20G from Version 1 WRX, it has the "divorced" IACV setup so I don't need to remove the intercooler.

    Still, it's not clear how you remove it, there are coolant lines going into it and all the info I find says "disconnect them", but how do I do this properly and safely and how do you put them back in and secure them?

    I'm also not clear how many lines need to be disconnected or are running into it, I believe there are just two.

    I'll try and post some pics a took a few weeks ago of the IACV area of the engine bay.

    If anyone has done this on EJ20G and can give some pointers that would be great. I'll include full pics and steps on how to do this once I've done it.

    I already have ordered a replacment IACV gasket from Subaru just in case too (not the entire IACV unit, just th gasket).
    Last edited by jdmvip; 11-03-2010 at 10:35 PM.

  2. #2

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    So did you ever get it off and clean it? Mine takes a couple tries to start in the morning. Where is this valve located?
    08' Ford F150 Lariat Crewcab 4x4
    92 Toyota Aristo full Bippu=SOLD
    92 WRX... lots of mods=SOLD

  3. #3

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    I haven't had a chance, I will probably try and remove it and clean it this weekend. I'll post some pics of it (I took some weeks ago but never posted them) and the lines that must be disconnected to remove it.

    It takes me a second try to start the car, but not to worry this is a VERY common problem and is usually cured by spraying the valve with brake clean, or perhaps more effective, soaking in gasoline.

    In rare cases you may have to replace the unit, but the good news is a North American one should fit, the bad news is that you're looking at a few hundred dollars. I still believe most cases can be cured with cleaning though.

  4. #4

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    Awesome, good to know.
    08' Ford F150 Lariat Crewcab 4x4
    92 Toyota Aristo full Bippu=SOLD
    92 WRX... lots of mods=SOLD

  5. #5

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    I'll post the pics sometime today.

  6. #6

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    IACV was a pain to take the bolts off, the bottom right most bolt is blocked by the intercooler. We had to take the top 3 bolt of the I/C off. We didn't remove the whole thing but shoved it up to the right by maybe 3-4cm (the tube below is accordion style). It would have been best to remove the whole I/C IMHO but there are 3 hidden bolts underneath the I/C on the right and unless you have a nice tool/perfect extension you won't be able to undo those 3 hidden bolts underneath.

    Still no pics, but with the help of civicless and my father-in-law we took off the IACV partially and sprayed the hell out of it with brake clean. It was so dirty you couldn't see the green flap/valve at all!
    The bad news is that the car still stalls on the first try in the morning, albeit less harshly and the second start is smoother and with no RPM hunt at all.

    I think the unit needs to be removed completely and more thoroughly cleaned. I bet soaking in gasoline like new age Impreza owners have done is the best way to go.

    This weekend we'll remove the entire IACV and soak it in gasoline for hours and see if that solves it.

    I'll try and post pics later today for sure, hopefully others have better luck. I'm sure this affects most Impreza's in general.

  7. #7

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    One more thing, the gasket I got was not a perfect match or fit (the holes lined up so I still believe it would have worked fine though, but it wasn't an issue because the original gasket seems just fine. The worries about replacing the gasket mainly come from newer model WRX's with EJ205 because their IACV is connected to the I/C and uses a rubber gasket which expands.

  8. #8

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    I don't have any update and I know I haven't posted pics yet.
    Has anyone had any success yet?

    My first attempt seems to have made things worse, I bet it's because I just ended up trapping more crap inside the IACV, which is why I'm sure the entire unit must be removed and thoroughly cleaned somehow.

  9. #9

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    Default IACV Images & Pictures

    Here's some pics to give people an idea of where the IACV is.

    The red squares are the IACV unit and the yellow squares are the bolts (sometimes you can't see the actual bolt), but there are two on each side (one high and one low).

    *Note the multi-tap power connector. If you are going to fully remove it, that must be removed too.
    *Make sure you take a picture of the IACV top plug of the angle and also the screw positions. You'll notice they are marked from the factory with white to give you an idea of where the screws are supposed to be. Adjusting the angle of the top plug on the IACV and the screws is said to adjust idle, so make sure you take pictures so you know how to line them up and how deep the screws are. Failing that, you could just adjust things until your idle is where it should be.

    *There are 3 hoses going into it, 2 coolant lines on each side and the clamps can be released by squeezing them together with a wrench.
    *The large one at the back I haven't removed so I'm not sure what it is for.....I'm guessing the obvious, air
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    Last edited by jdmvip; 11-09-2008 at 11:03 PM.

  10. #10

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    Default Pics of the process

    Sorry took these a few weeks ago too but no time to put them up.
    Here's some select pics.

    If someone can recommend a tool to get to that bolt for the IACV which is mainly blocked by the IC it would be appreciated (you'll see what I mean in pic#3 look at the bottom right bolt being blocked by the IC). There is such little space I have no clue what would fit. I guess maybe a ratchet with a very long head or extra long but skinny socket would work maybe.

    *Sorry for poor quality closeups, I didn't know what Macro mode was until a few days ago lol

    Thanks to civicless and my father in law.....none of those hands in the pictures are mine. But at least I'm learning by watching
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    Last edited by jdmvip; 11-08-2008 at 05:21 PM.

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