My girlfriend has got a Astra mk3 1.6 16v (x16xe - i think?)
Its been playing up big time. Most of the time it wont start and when it does its chucks out loads of black/dirty smoke and revs 4k+ on its own. Also when going along (any speed) if you take your foot of the gas then back on again it judders quite bad. It's also got next to no power.
Any ideas? Someone told me it could be the idle air valve?