hello tabetha and cheers for the reply

its the water temp sensor WTS09 which is discontinued so went for the appropriate OE one..

Whats happening is no matter what sensor is screwed in to thermostat housing it idles poorly when connected correctly but when you disconnect that sensor and connect one that JUST HANGS in the engine bay ..so as in open air...it idles like a dream..

After putting the car back together it was mint untill 10 mins down the road. then all this

Ok after doing a dash test im getting a P117 error code which means temp sensor voltage is low. DOes this mean the ECU is sending a low signal? but then that contradicts what is happening when i leave a sensor (whether its duff or not i have three new ones here AND ONE DUFF ONE) connected but not in thermostat housing....