On my 89 GTI I have found that adjusting the mixture adjusting screw on top of the flow meter OUTWARDS by one full turn decreases the CO reading by 0.66. I assume that yours is not cat fitted.
So if you do the maths....then if you adjust your mixture by 7 turns you will get a legal reading. If however you find that the tickover is weak and irregular then the mixture will be too weak and then screw it back in until the tickover sounds more regular and normal.
Alternatively ask the garage to adjust the mixture to give you a pass reading. It only takes a few minutes.
Emissions fail - advice please!
Moderator: RichardW