Failed emmissions
 

1984 Porsche 911 3.2
Took it out of my garage today for first time in 4 years .Took it for its MOT.And failed on emissions Co 12.5.
Last time i took it which was 4 years ago it passed.Since the last MOT and this one it has only done 300 miles inbetween mots.

Old gas ?

Old gas, old oil.

When I failed emissions in the US in an 85 non-US 911, the car needed an oil change and I on,y drove 5 minutes to the inspection station. A mechanic told me to change the oil and make sure the car was warmed up throughly. Went back under these conditions and passed with flying colors.

I changed oil,
Drained fuel put new in.
Took it out for about an hour ,give it a bit of stick to give it a clear out..
Very strange as last time it was perfect.

David -- still think this is linked to the issue you raised in your other post regarding a bouncing idle -- both high CO and bouncing idle are generally caused by too rich of a mixture. While there are a few threads that discuss how one can set the mixture by measuring the voltage from your 02 sensor, it's likely best to have a 911 knowledgable shop do it with proper sniffers/procedure.

David, after 4 years I would do a complete tune up with fresh oil . 40 pounds in the back tires . Drive the hell out of it before shop does the test .