What's an ISV?

[M96DGT]

Hi all!

Can anyone tell me what an ISV is?  I've been checking the posts to try and find info to sort out my stuttering Mk3 8v GTi, and the ISV keeps being mentioned.  What is it, where is it and any ideas of replacement costs/repair/treatment?

I've been doing a bit of spring cleaning around the engine to try to improve the running of my beast, as it has always been a little hesitant.  I've replaced and cleaned some of the oil breather pipes, cleaned the MAF sensor in petrol, cleaned out the throttle body, and replaced the plugs and leads.  It does seem a little better, HOWEVER, on returning home this evening it seemed a little lumpy and the tickover was high at about 1400rpm.  Can anyone point out my mistake?

thanks all!

[...joe]

ISV = Idle Stabilisation Valve. tube on top of the rocker cover that vibrates when the ignition is on. plugs into the breather one end and the inlet the other.

[mark3valver]

its the thing you can see at the front of the manifold

[M96DGT]

Thanks!  The picture looks like a 16v engine, I'll have a look for something similar in my 8v motor, unless it is different?

[perryqhill]

Thanks!  The picture looks like a 16v engine, I'll have a look for something similar in my 8v motor, unless it is different?

Should be on top of the rocker cover on a 8v IIRC.