I have a S60 2.4T and would appreciate any help. When the engine is cold the idle is ok, once it warms the idle becomes very erratic. On the way into work it stalls twice at the same place each day. This is not a new problem and when it was being serviced by a dealer they said that they sprayed something? around the engine bay and this cures it for a year. I am now not using a dealer (to expensive) but my mechanic can't seem to cure the problem. Any suggestions would be helpful.

Update:

I have changed the thermostate since writing this and the problem has got worse...