Opel Vectra burns oil

Thank you for a brilliant site.
Car burns about a litre of oil every 2000 kilometres.
Have an error code 0171.
Idles high on start up otherwise runs fine.
Been going on a while, do not want to inflict
any more on the car.
I am reasonably handy and have done a lot of research, (and looking).
Having a good mechanic doing a diagnostic tonight. (Has just cancelled till next week).
Don't expect an answer from you guys based on above little information.
Really write to say your site, your site is a Godsend.
To think you give such help that I will use,
for free is amazing.
After having a very bad experience with work
a mechanic lately.
Will report back if possible.
Thank you again.