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[Diamond Black Geezer]

Slightly shakey idle from time to time, generally diagnosed as a vac leak, of course. Couldnt find any leak anywhere, so thought let's try replacing the ICV. Got a spare, cleaned it up till you could probably confidently drink a fine wine from it. Swapped it over first thing this morning.

Before:
P and D 500rpm, slightly lumpy, and sometimes wavering to maybe 480/520rpm

After:
D 750rpm
P 1000rpm!!

Only thing I did is like a silly sod I forgot to plug it in before turning her over, so I quickly plugged it in whilst the engine was running, Have I 'reprogrammed' something here in doing this, or is it all down to what must be a bad ICV?

Oh, now at work and guess what I didn't bother to bring with me? That's right, the original ICV!

[frostbite]

Your after results should be the other way round

have you got a throttle cable?

it might need adjusting

ac should raise it to approx 1100rpm

[minifreek]

Always replace the ICV, cleaning doesn't work.... in my experience anyway

[Bojan]

IME, runing engine with unpluged ICV doesn't leave any consequences.
The spare that you've installed, maybe it sat too long, and it seized a bit.
If you have some penetrating oil, try spraing some inside the ICV.
 
When you get back home, put in an old one and see what happens (I'd bet it will run around 500 rpm idle).

PS. It has a throtle cable. ICV and throtle cable go toghether (on Omega)

[Diamond Black Geezer]

Thanks 

ICV, both 'new' and old are free and moving very nicely. Replacement hasn't sat at all, and got a shot of light oil just to be sure. Bladdy shame, as it's soo clean!!

Another thought I had was potentially that being unplugged momentarily meant the ECU had to 're-learn' the position, or something, but that looks like not to be the case.

Now I come to think of it, that ICV might be the one that was fitted when I was having all those poor, and high idle problems while she was still SORNed... which turned out to be a number of things, air leak, knackered HTs, knackered coilpack, badly adjusted throttle body and I think I may have also replaced the ICV.... hmmmm 

[zirk]

If youve cleaned it with Carb / Brake cleaner ect, then it will run rough (normally high reving) until its settled down, take it for a good Italian.

[X30XE]

Had this on a volvo V70 recently.  Cleaned the darn thing and made it worse.

Some tonka had adjusted the end stop on the throttle butterfly to compensate for the dirty ICV.  Check the throttle closes fully (or at least as far as it's supposed to go - can't remember if the omega one is supposed to be 100% shut?) . And clean it while you're there.

[TheBoy]

Check for other airleaks, including the butterflies (which should perfectly shut)

[BazaJT]

You did check for air leaks around the rubber grommet that ICV pushes into didn't you?Checked that it's seated properly?If you need another ICV to check I've got one here

[Diamond Black Geezer]

Swapped back for the original all well(ish!) again. As per exactly what Bojan said - it was seized!! Happy to accept some egg on my face, here. However, I'm amazed it was, it got cleaned so thoroughly and with some light oil as an extra measure, thought it was moving freely. Anyway, I've had it soaking, poked around and got it moving again, it now moves very freely. Will have a look at swapping it back again, however, given it's seized on me once, I might not bother leaving it on.

Tonka - throttle body poorly adjusted was one of the reasons (as listed above) she didn't run right when I got her. Replaced with a good, low mileage TB, which has a dab of yellow Opel paint showing the screw hasn't been tampered with. Fully closed and back 'a bit' is, I think the Patented Marks DTM method of adjustment.

TB, thanks for the heads up, I never considered the butterflies as potential cause for airleaks. Will have a look. Reading Webby's post the other day I see they're interchangeable, which is nice to know, as I have a whole spare plenum which was pretty much going in the bin, but if the servos/butterflies are worth salvaging off it, as spares, then I will.

Baza, thanks for that, it's very much appreciated, I've actually got another spare, which I managed to find this evening. There's a mint 2.2DTi FL in my local scrappy, if there's anything at all you can think I might be able to get off it for you ( - very nice nick black steering wheel, for instance) in Z157.

My main worry was in leaving unplugged I managed to 'reprogram' something, as I've never been thick enough to forget to plug it in before. 

Will report back when I've had chance to check out the butterflies and for other airleaks. Most likely around August 2023 

[BazaJT]

Other than centre caps for the wheels-which I believe we've already established are different-then I'm hoping I've finished spending on bits[at least for now!]next step is paying out for someone to come and fit them all for me!

[Webby the Bear]

DBG don't throw a spare plenum away!!! Comes in very handy. Trust me! 

I'm sure over the years we've had many discussions about vac leaks. Have you checked the two o rings going from the breather in to the top of the TB? And of course don't forget the 'top hat' seal between breather and plenum.

I know people will disagree (and I can only comment on what I see) but the OE o rings from breather bridge to TB are too thin and I've had air leaks on both sets I've used. I 'upgraded' to slightly thicker o rings from a generic set you can buy online and hey presto, no air leaks 

[Diamond Black Geezer]

I reckon that is high on the likely places for an air leak, actually, Webby, you know. Now the nice weather is happening tracing such things is a hell of a lot nicer than a few weeks back, when I was working on the spare Omega and managed a hefty 12 minutes before my fingers went numb.