Black smoke coming from oven while preheating

If you are getting soot residue, it could be a number of things, First, is this a natural gas or propane oven? If you bought an oven to be used for propane, it may need to be converted from natural gas to propane or it will soot everything up. 2nd, have you recently spilled food/liquid onto the oven burner? If the burner holes are partially plugged, the remaining holes will burn large yellow flames and soot up the oven. Check the burner flames, they should be mostly blue with little to no yellow tips. Also make sure the oven burner flames are not too big. They should never exceed the width of the flame spreader pan directly above the burner, in fact they should be less than half the width. You could also have other issues like improper air shutter adjustment to the oven burner or very low regulator pressure, but most likely it has just been spilled on recently.