CAT warning light on Audi S8 - Daedalus
Hi there folks one of my very rare postings these days, hope you are all ok.

I have got the loan of a 1997 S8 for a couple of weeks with a view to buying it. It is totally kosher 120,000 miles with full history, it is coming from one of my suppliers so I know that he is being right up front with any issues with it. Today the CAT warning lamp came on and the engine started to run really rough, it then cleared again and was ok until this evening when it came on again and the engine was rough as if it was missing. I was wondering if anyone had any experience of same and what the result was, new CAT's I don't want to think about, maybe a Lamda sensor somewhere! Anyone any idea of costs of these or can think of any other issues.

Many thanks

CAT warning light on Audi S8 - Screwloose

You've probably got the emission [cat] warning light up because it's missing and running rough and that is what's upsetting the oxygen sensors. Could be a whole plethora of things causing it; but a good start would be to check the coilpacks or the signals from the ignition amplifiers. [Depending on exact fitment.]

Simply getting the fault-codes read would be the best way. Don't drive it with a misfire or you may well end up with a new cat. [Not sure if Kwik-fit do those....]
CAT warning light on Audi S8 - jc2
Too right-serious misfires can kill cats.
CAT warning light on Audi S8 - robert
Could be HT leads. These are VERY expensive on the A8 .........


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