Faulty range/oven parts aren't the only worry a gas range owner has; the threat of carbon monoxide is very real and should be paid close attention to when doing repairs on the range.
If your range or oven gives off soot, you definitely have a carbon monoxide problem. Soot is the result of inefficient or incomplete combustion. There are always elevated levels of carbon monoxide with soot production. Properly adjusted range/oven parts do not give off soot. You may have poorly adjusted gas pressure, the air shutter may need to be opened, or you may be supplying fuel the oven isn't designed to handle. Don't use natural gas in liquid propane stove or vice-versa.