The emission warning light came on on my 1991 945 with the 2 litre non-turbo engine. I was a couple of hundred miles from home so I drove back with a slightly lumpy running engine.
The exhaust and plugs are very sooty black so I am certain the engine was running very rich after the warning light came on (running perfectly beforehand).

So my question is: Will all of that carbon in the combustion space and exhaust give me any problems if I just replace the lambda sonde and the catalyst? (I am assuming that the cat will be damaged by all that sooty carbon so intend to replace it).

My concern is that the sooty carbon in the combustion space and the exhaust upstream of the cat will simply ruin any new lambda sonde and cat that I fit. Do I need to do any cleaning up (if that's possible?) to remove the carbon?

Thanks for any informed advice!

Best regards

OwenF