Volvo Repair: Volvo C70 misfire, volvo c70, coolant temp

Question
Hi Roger,
       I own a 1999 C70. About 1 month ago it spluttered when starting from cold. After about 20 secs, it runs fine. It seems, the car has to be stood for around 8 hours or more for the fault to appear, anything less and it starts fine. I changed the plugs and bought a new coil pack which i tried on each cylinder but the fault remains. Two independant garage diagnostic sessions only revealed a misfire code but it wasn't specific to a particular cylinder. Any ideas what to try next ??
Thanks in advance.

Answer
Antony, if its happening cold then its possible that its overfueling first thing then straightens out.  I would replace the coolant temp sensor.  Its on the thermostat housing.  If the sensor looks green and corroded, then definately change it.  Let me know how it works out and then we can go further.  Roger