Soot on bumper after Vanos work?

[chris719]

I just completed a vanos job on my Z4M and in the process replaced the PCV. Other than that it was all just cleaning and replacing the necessary items. Started up and ran, drove around and then did a Vanos test. Test passes but after the test I noticed a decent amount of soot on my rear bumper, more gray than black. Is this something anyone has seen before?

[bigjae46]

Maybe running a little rich as the ECU adapts?

[chris719]

Maybe running a little rich as the ECU adapts?

Yeah, I cleaned it and will keep an eye on it.

[maupineda]

It would need to run extremely rich to soot the bumper in one drive cycle unless it was a looooong one. Maybe it was there? Or just road debris / grime? Tail pipes look ok. Not sooty

[Slideways]

[chris719]

I washed it and drove about an hour and it came back a bit but less. It could have been there but I haven't really noticed it before. It's not black soot like your typical rich running, more light grayish. Will just keep an eye on it for now. It just seemed to be distinctly visible right after the Vanos test, which could be coincidence or maybe not - it does have some interesting behavior during that test.