how can i fix my vauxhall vectra 2.5 v6 1997?

Sounds like it might be the idle control valve being clogged up, locate a manual for your car to find the position of the idle control valve, remove the valve and give it a good clean removing all the oil and gunk from within it and replace back on the engine, this should now send the correct signals back to your ECU thus allowing the engine to turn over correctly. You may also wish to check that all spark plugs are recieving an adequate electric current and are sparking correctly.

Michael
November 2006