As part of my quest to get my 1.9 CDTI 150 to run a bit better I thought I'd take the throttle body off and see if it needed cleaning.
The first pic shows the throttle body location. Pic is courtesy of the_wizard (cheers mate).
I took it off and split it apart by removing the clips. It wasn't too dirty, but I cleaned it out with WD 40 and re assembled it.
Link to how to clean the throttle body.
When I went to put it back on I noticed quite a lot of black gunk on the intake, so I thought I'd clean that up as well. Unfortunately I didn't take a picture before I cleaned it, but I thought it might be worth showing what it looks like now.
On the picture the blue arrow is pointing to the EGR valve. When I had this off to clean it I noticed a lot of black oily gunk in the two holes going into the manifold (red arrows). I cleaned it up, but didn't realise until I had the throttle body off what was going on behind the holes.
The yellow arrow shows the machined face where the throttle body goes on tio the end of the manifold. Notice the holes through to the EGR, and the curved walls that come up to the level of the machined face. With the throttle body in place these walls form a channel through which I guess the gasses coming in from the EGR travel (green arrows). I'm assuming the curved shape and the gaps have a kind of swirl effect on the gasses.
Anyway, this channel was completely full of oily gunk, all the way around, and all the way up to the level of the machined face. Everywhere there are green arrows was solid gunk, meaning that the gasses from the EGR were severly restricted.
It took quite a bit of scraping out with a small screwdriver and spraying with carb cleaner. I put a rag just below it to catch the dirt, and there was a load of it.
So it's definitely worth having your throttle body off and cleaning the inlet if you do the EGR clean. Even with the EGR valve working perfectly the deposits inside the inlet might restrict your low down performance.
The screws were a bit fiddly to put the throttle body back on, and I dropped one. Heard it rattle down and stop, but after 20 minutes getting the under-tray off it was nowhere to be seen. So it's in there making friends with the torx bit I dropped when putting the Boost sensor back after cleaning that. (butterfingers!) Luckily I found a suitable spare.
Since doing this the car ran better up to 1800 revs but there was another problem I had with a split pipe which was stopping the turbo kicking in properly. (see http://www.vectra-c.com/forum/showthread.php?t=109454)
Hope this helps someone.