mk3 gti cuts out when cold

[hughesy]

 Hi guys! when i start my cold engine and drive for a minute or so i step on the clutch and watch that rev counter drop down to zero and my engine go back to sleep! 
My temp gauge never gets to 90c so i presumed it was the coolant temp sensor which i changed yesterday. drove the car and the gauge went to 90 and no engine cut out so i thought problem solved until i drove the car today!  any ideas? 

[Diamond Hell]

Check your earths and the power connections around the engine bay, take off the inlet trunking and have a look at the throttle butterfly.  If it's got nasty black sh*t all round it, clean that up and you may find it idles a bit better.

If these changes don't improve it, scrap it.