Rough running on tickover

Hi all,
Ihave a 2001 td5 which has developed a strange intermittant problem,sometimes on tickover the temp gauge goes to the bottom and the high temp light on it comes on, the engine also ticks over quite high and hunts a little, sometimes its fine.
just looking for any ideas to what may be causing this?
any help appreciated.

Thanks Ross

check the connection at the coolant temp. sensor, if it looks OK replace the sensor... this sensor's inputs are used by the engine management too so if it has erratic behaviour the ECM may limit the fueling then

Have a look at the red plug and socket on the main ECM in the engine bay, if it is contaminated with oil give it a good clean with brake and clutch aerosol spray and allow to dry.

Put the ECM on it's end on some paper towel and allow to drain and dry.

Test drive and assuming it is improved, you will need to replace the injector loom O-rings - cost approx £2.

cheers for the replys, will try the coolant temp sender got another disco sitting there ,the ecu is dry&clean

changed the temp sender ,now shes runnin sweet
cheers for the help