Still got a cold idle problem on my MY98 WRX and the last thing I'm going to look into is whether the idle air control valve's bottom end if functioning properly. Electrically (the top end part) it's fine - it reads the correct impedance each way, the magnet is working, it idles and returns to idle absolutely perfectly when warm. I've got it off now and the shaft opens and closes the chamber properly, no obstructions there.

The thing is though, it's not just an electrical device, although this doesn't seem to have ever been discussed even once on Scoobynet. The IACV has water pipes that run through the bottom of it, which heat up a bimetallic strip which then actuates an air cut valve. According to info I can find on it, this should be wide open when cold and gradually close up as the water temp starts to rise. The water passage through the valve seems to be clear.

If the air cut valve is stuck or not working, it would explain why it idles spot on when warm, but in the recent cold weather we've had it's been stalling and hunting on idle. I've tested all other sensors and they're all fine.

So here's the problem - how to dismantle the thing properly? It's easy enough to take the electromagnet bit off the top. Should the bottom bit (sealed with a ring of silicone) come off? Should the main air inlet pipe be removable? Because then I could get at the mechanicals and see if it really is opening and closing this air cut valve correctly.

Help!

 

Anyone?

 

ive tried to have a go at the one on mine, but i couldnt work out how to open it up, in the end i just bought a one from a scrappers. for £40 cos subaru charge £280

 

Yeah the crooks, they wanted the same out of me. No way I'm paying almost £300. But then the problem is getting one from a scrappies, there's no way of knowing whether it's got the same problem.

I've tried running cold and boiling water alternately through the water pipe and when hot it definitely does close up the air passage. THe thing is when the thing's cold it doesn't seem like it's opened up a great deal, which could be the cause of the cold idle problem. THe other thing is, without getting either the bottom off or the air inlet pipe off, it's very hard to check if the air cut valve is moving and where it's at. From the workshop manual it looks like the hole is supposed to be fully open when cold, and it's definitely not doing that.