The year and mileage of your Vectra would help. If you are in the UK it must be a 1995 or newer model.
If you are in the Uk stop by the Bason Bridge Garage. It is about 3 miles from Burnham-on-Sea in the West Country. Dereck the owner is a super mechanic and great guy. He is partial to Little Debby snack cakes. :Lol:
I would start by checking for vacuum leaks. Look at all the hoses and connections. Replace any that are cracked and brittle or soft and gummy.
Next check the IAC (idle air control) valve. If the connecction is good, test it and then clean it and it's port.
Good luck and lewt us know. :)
Tuesday, April 4th, 2006 AT 7:00 PM