Remove, strip and clean the throttle body and idle air control valve. On later models the IAC valve is part of the throttle body so cannot be cleaned seperately. If cleaning does not work you may need a new IAC/throttle body.
Use new gaskets when re-fitting, only a few pounds from Vauxhall dealer.
Clean using carb cleaner available from halfords/motor factors. Make sure all the breather holes in the TB are clear, including the little one under the butterfly.
fly, April 2012
