Failed MOT, high CO

[pilot4fn]

Originally Posted by Robert986

Thanks a lot, great input!

I did heat the cat:s quite a lot before MOT, when it failed I got a chance to heat them more and went for a 20 min very VERY spirited drive.. Still the same values at 2500rpm, 0,7 on bank-1 0,5 on bank-2.

So I have a feeling there is another bug somewhere..


Idea-1 -Can it be that the gaskets provided with the ebay-headers are of low quality so there is a small air-leak before the pre-cat O2 sensor, thus giving a slight rich condition? (however lambda after cats tells different) Would a slightly rich condition pre cat be mitigated by the cat to give a good lambda in the tailpipe?

Idea-2 -Could it be a leak in the AOS, so I get a lot of oil residue in the intake? Will check that tomorrow. Spent today with cleaning up in the garage to give room for further examinations.

I'd believe that both ideas you mention are feasible.
Easier to check first is the AOS failure. As the engine is warm and idles, open up the oil cap in the trunk. If it has a very high vacuum (I guess hard to lift the cap), then you'll have most likely a failed AOS.
Also, the inteke plenums would have oil inside if AOS has failed.