Strange problem feels jumpy!

[Timlowthian]

Hey i own a 1.4i westcoast and i have noticed a small problem that is bugging me.

When you are driving along normally then you take your foot off the accelerater to free wheel for a bit as soon as your foot comes off the accelerator the car jumps a couple times then is fine.

I also noticed the other day when i turn it on sometimes it revs up and down quite alote before settling at 1k.

Any ideas what could be causing this?

[James205rallye]

Sounds like a fuelling issue to me but am not sure what to be honest.

[Timlowthian]

Well when i bought the car i found that the lamda sensor was unpluged so im wondering if that was for a reason? maybe replacing that could help?