1991 Audi Coupe with 7A motor - 360,000 mile service finding

[cgharibo]

I am in the midst of doing 60k mile service on my 1991 coupe with the 7A engine. The car runs like always, slow but good and does not burn oil.

I took the plugs out to change and they all look great. I put a scope in the plug holes and I can clearly see black carbon deposits on all the pistons.

So how do I get rid of these carbon deposits on the piston head or do I just leave them? The newer Audis that burn a ton of oil are subjected to Berryman B12 piston soak where the solution is left in for like 24 hrs. Should I do same piston soak, do something different or just let it be and put new plugs in there and move on.

Thank you!

[K Simmonds]

If it's running fine as indicated by the colour of the spark plugs I'd be inclined to leave the contents of the cylinders well alone, a light coating of carbon on the piston crowns is completely normal with a naturally aspirated engine and not an issue.

[Bowie69]

Yup, leave them.