Is the coolant circulation through the bottom of the ISCV purely to prevent icing up or is there something else? Mine was bypassed when I did the throttle body a while back but I'm now wondering if I did the right thing...

 

It's used to adjust the idle speed on tickover, Relating to engine temperature Etc. The colder the engine, The more open the valve is & a higher tickover speed.

Dean

 

So, if it's disconnected presumably it will take longer to settle down to it's normal idle speed from cold. I think that I might connect it up again. Cheers, Dean

 

Something Ive learned today cheers always wonderd what was its purpose

 

It's a water passage that heats up the 'air cut valve' which rotates to close or open up the main duty valve (itself controlled by the electromagnet on the top). It's basically assisting with the auto choke function on cold starts.

 

So normal hot idle won't be affected, then. Damn. I'd hoped that it might be a solution to my idle problem - the usual dropping to 500 before rising to normal or sometimes cutting out altogether. I've tried all the usual fixes here - what is it with these damned things that makes them so temperamental

 

Yes it could be. I had the biggest problem when it was cold, but it still occasionally did it when hot. Just gradually worsening weird idle problems. In the end after trying everything else, I just got a replacement off a scrappies and fitted it. I was gutted when I first went to start it up and the idle was all over the place, but it must have been just the Power FC learning new settings because the next morning, and ever since it has been absolutely perfect, like a new car.

A modern car should not struggle to idle smoothly, whether hot or cold. If it does, there's something wrong.

 

I always thought that it was purely a de-icing water circuit, RCMS bypassed it the last time I was there for some work and hasn't made a difference

Shaun

 

It may well work ok without it, but if it gets stuck shut (or open, I can't remember which), it'll always be a pain. Anyway it's a coiled bimetallic strip that swivels a little wall around in and out of the air path through the duty valve.

 

I think your thinking along the lines of throttle bodies, Where fuel , Air & Moisture vapour may freeze on V cold days !! Used to be & is still a problem on Twin 40 Dellorto Type carbs,

Dean

 

any more news on this?

 

You used to get some kind of similar thing on Beetles to stop them icing up. Anyway, if you have a Subaru technical manual you can see the cutaway diagram of it shows pretty clearly how the bottom part works.