I currently am waiting on my Bluetooth elm 327 scanner to come in. While doing so, I figured I would research what all could be causing my issue (rough idle, bad gas smell when windows are down/ reversing into area I sat for a minute, black smoke, tailpipe black). I first was told to check for vacuum leaks, but since it runs rich I am unsure if I should do this. Autozone says it is the maf. I unplugged the maf, but it idled roughly with it out so I plugged it back in. About a month ago, I greased my driveshaft. Maybe 1-2 weeks later, the rough idling began. When I went under my vehicle, I noticed one of the downstream 02 sensors in particular was covered in grease. I wiped it off, and now it has some burnt residue still on it. While my issues are still very much there, it isn’t as violent as it was when it first (very randomly/ almost coincidentally) started. I wanted to ask with all of this updated information if the grease could have caused the issue by clogging up my 02 sensor? If so, I might replace the 02 sensors (even if they’re less than 15k miles in), to make sure they’re all new and clean. Thanks for anyone who responds, it might be a dumb question but it just seemed very coincidental.