Brilliant! That really is one of those things that no anount of forum time will diagnose for you :mad: Its a great feeling, I found this through troubleshooting my own car which turned out to be the electrical contacts in the AFM. Similar you you having an easy fix in the end, I just wish it was eas...

The fueling ratio changes depending on the air coming into the engine. If the AFM isn't reading correctly, fueling wont be right and so can run as if theres a vacuum leak where the engine is getting more or less air than it thinks it is. Idle is controlled by the ICV, but the air passing is still en...

Issue resolved :banana: Turns out the carbon track in the AFM was worn (although to my semi trained eye, it looked fine) I bent the electrical contacts so they contact a fresh part of the carbon track and hey presto. A smooooooth idle :cool: After convincing myself further that I had a vacuum leak, ...

Right... where do I start :roll: I've tried to format this post to make it easier to follow with the history first and my questions at the end :P My 1991 M42 will start and idle 100% when totally cold, but after about 30 seconds the revs will decline to about 500rpm, at which point it sounds like it...

I would imagine that the internal shock themselves are different in size too but could somebody confirm this..
cheers