Hi all, a bit of a different theme on the "normal" idling problem:

- my 16V XSi (XU10 J4R engine) had a problem a while ago, where the plug at the back of the inlet manifold came loose whilst driving, causing stalling whenever I pulled to a stop.
- In my attempts to rectify this (I didn't spot the loose connector for a while!), I replaced the lambda sensor, removed and cleaned the throttle body, and replaced the stepper motor (idle air control valve). Only on finally plugging in the new ICAV did I spot the errant connector - grrr!

However, since reconnecting that plug, the car "hunts" like mad whenever I start it, or roll to a stop from driving (varying from 1000 to 500 revs, 2 or 3 times before settling). It occasionally gets so bad that the dip in revs causes it to stall, although this is unusual. I can't be sure, but it even seems speed-related in some way i.e. when it finally settles, just lifting the clutch to crawl off in traffic seems to upset it and start the hunting all over again.

I have checked and double-checked that I reconnected all the plugs to the TB, and looked for an air hose come loose or split, but to no avail.

(The only other thing I have recently done is replace the back box - there is still a slight leak from the cat/centre pipe joint, but I can't believe this would be enough to cause the kind of idling I am experiencing.)

My first thought was that the ICAV is mismatched in some way, so I will replace the old one initially to see if that helps (seeing it wasn't the cause of the original problem after all). But if that makes no difference - I am stuck! Any ideas?