In middle of vacation, suddenly black smoke pulling away from stops
Usually I'm right around sea level, this week I'm on vacation in the mountains, 5k-10k feet elevations. Pulling a pretty light trailer... 3k pounds. SuddenIy I'm getting large puffs of black smoke pulling away from stops. No change in engine performance. Exhaust looks clean after the initial black puff. No recent mods except the cat or particulate filter or whatever its called is back on since I took it in for a smog check recently.
Any ideas? Thanks!