[cooked]

Hey All,

New here; not new to BMWs but this is my first N55.

Last fall my son and I picked up a neglected 2014 X1 35i for a great deal as a project to work on. It's been fun and we've fixed all of the common N55 issues, including replacing the VC, OFHG, both O2 sensors, and giving it a full and proper tune-up. We have almost 2k miles on our repairs, and the car runs great, has an even idle, no codes, no vacuum leaks, nothing odd, except that post fixing all of these things, the car now has a puff of dark smoke at startup, only when cold and only after sitting overnight. It's definitely not condensation and doesn't appear to be oil (not blue / greyish, and def looks dark like rich combustion), and is only there for an instant, possibly associated with the first fire of whichever cylinder(s) are rich.

Most likely it's a leaky injector, maybe due to disturbing the fuel system by removing the fuel lines over the VC and introducing some debris, or maybe just from age. Or it's possibly downstream of this (dirty combustion chambers that need to be walnut blasted; fouled cat from running with codes? Who knows....). As it does appear to be fuel, from searching around, likely next steps are to pull plugs when cold to see if any of them have fuel on them and/or are gas fouled. I'm hesitant to do this and just keep driving it to see if it cleans itself up, but before I go that route, I thought I'd make a post and see if anyone has chased this issue down previously. Rich is better than lean, but if this is an indication that there will be a bigger issue if left alone, I'll be more proactive in digging in.

Thanks and appreciate any feedback.