since your car works fine, but just has some small kinks, before you bother tearing stuff apart & buying new parts.. why not do the easy thing and get
-seafoam
and afterwards
-lubro moly fuel injector cleaner
that's like $17 total and doesn't require any labor
bad idle = good chance its dirty injectors
but that doesn't explain change under weather
clogged cat? (which works better when warm). seafoam cleans your cat
ofcourse you probably dont have a cat in the netherlands but it helps with throttle response
also low battery = bad idle. and cold is bad for batteries. sometimes in neutral you have to keep it up with accelerator or it will stall.
you're probably not some idiot with a bad battery but seriously if you make a lot of short trips, it will get low on juice and give you shit idle
theres always coil on plug kit!
http://m42club.com/forums/showthread.php?t=9122&highlight=coil+on+plug coil on plug solves everything :confused: