I am looking after a friend's cars while he is out of the country for a couple years. One of them is a '99 Passat (1.8T AEB engine).
One of the monthly things that I do is get the engine up to temp and drive it back and forth to put things under load and exercise the brakes and clutch. Since it is in particularly space that whole time, water vapor from the exhaust gets left on the floor at the tail pipe exit. Unlike the other cars, the Passat's exhaust is leaving a carbon residue on the floor after the water evaporates. I checked the plugs and they look good. The tailpipe itself doesn't have carbon build-up.
Anyone here know what's up?