Having read the horror stories, I decided to try a DIY job on the
of my Scenic 1.9DCi (89k miles).
To get at it, I only had to undo the left end of the air filter housing.
The three bolts came out very easily, however, as mentioned in another thread, it seemed solidly stuck in place to start off with. I started off by giving it a few judicious taps with a light steel hammer, then tapped the flange sideways to rotate it, successfully (Care needed, as the aluminium could snap across the bolthole).
I was able to waggle mine out a little way with the strength of my grip; I was then able to get a screwdriver in behind and lever it gently the rest of the way.
Maybe I was lucky -- this was all done with no damage to the faces or the thin steel gasket.
Here is what I found:
Despite the heavy coking, the valve itself seemed to be moving freely, but it is easy to imagine a further buid-up or a lump coming loose and jamming it, one way or another.
I didn't use any solvents, for fear of getting them into the solenoid. I just cleaned it up with a wire brush and an old screwdriver.
Without interruptions the whole job would be a couple of hours.
I'm passing the time doing this thread while waiting for a thunderstorm to pass, then I'll be putting things back. I don't suppose there will be any noticeable difference, but I'll add to this in a week after some holiday running.