Clean the mouse nest out of the air cleaner.
carbon monoxide is in exhaust gas
Engine exhaust.
If you are a mechanic you should know the procedure.
carbon dioxide
It comes out of your exhaust, in the engine it combusts making your car propel forward, the vaporized gasoline exits your exhaust.
The black gunk that comes out of the exhaust pipe when starting the car is probably carbon buildup within the exhaust system. Carbon buildup happens when the engine is not burning fuel as efficiently as it can.
Carbon monoxide comes out of a car. This colorless gas that is released from a car's exhaust is poisonous when inhaled in a highly concentrated form.
Neither. It's a vapor (gas).
Exhaust leak? Vacuum leak?
Oxygen which comes out of a car exhaust is a product of reaction in the catalytic converter. In the catalytic converter, oxides of nitrogen undergo reactions to form less harmful nitrogen gas and oxygen, which are then expelled through the exhaust system.
look under the car at the exhaust. from the front of the car, the pipe comes down from the motor the converter should come next. it is a wide flat piece the looks like a flat muffler.
It's probably oil, and you need to get that checked out immediately.