petrol 1.8 freelander 1

Hi guys,it seems the problem is getting worse and thought I would put it pass the forum to see if there are any suggestions,recently when I start from cold I have to keep my foot on the accelerator as it wont fire up by itself as it used to do,when it starts if I hold the revs at 1500 for a couple of minutes it will idle at about 1000 and stay there but if not the revs drop immediately to zero and it stalls.It always started well before and then the problem started whist driving a while ago it started to shudder suddenly and felt like the handbrake was on as it had hardly any power,so I just let it tick over for a while until it calmed down and was drivable but has been smelling of petrol and is rough to drive since and of course it failed the emissions test at the m.o.t results were lambda 0,883 and co 5.11%.The engine management light is not on .Any suggestions would be well appreciated as I don't want to go and change all the sensors and still have no joy.cheers Mike