[teamilluminata]

I suspect my IRIS valve is faulty as I am getting stumbling and hesitation upon acceleration between 2000-3000rpm. I know there are other possible causes but want to rule this out.

I have read, probably on this forum that it is open at idle, closes at about 2000 and opens again a little above 4000rpm. I've also read that you can check the opearation by watching the actuator move while operating the throttle by hand. I've tried this but can not see enough under there to tell if anything is moving. I can snake my hand under there and feel the actuator rod but I only felt it move slightly when blipping the throttle quickly. It hasn't moved yet while reving the engine but I can't do that and see the tach so I don't know how high the revs get but it is bllody loud and hot. I also don't know which position is closed and which is open. My rod moved slightly towards the drivers side when I blipped. Is this opening or closing the valve?

Any other tricks to checking this thing?