Lumpy Omega

[Mike100]

Hi we have a 2.6 V6 Vauxhall omega on a 51 reg and it has a little problem every time youstart it the car runs fine but as soon as the temp gauge starts moving it runs really lumpy and very nearly stalls all the time until the temp reaches about 90oc and then it runs fine again it also has new spark plugs and new coil packs on it but is still does it.
the emission light comes on and stays on all the time now we have had that diagnostic code problem computer put on it but it only come up with missfiring which has now been sorted.
Does anyone have an idea?

[2 litre]

Hi we have a 2.6 V6 Vauxhall omega on a 51 reg and it has a little problem every time youstart it the car runs fine but as soon as the temp gauge starts moving it runs really lumpy and very nearly stalls all the time until the temp reaches about 90oc and then it runs fine again it also has new spark plugs and new coil packs on it but is still does it.
the emission light comes on and stays on all the time now we have had that diagnostic code problem computer put on it but it only come up with missfiring which has now been sorted.
Does anyone have an idea?
sounds like the temprature senser has had it mate:(