What do car fumes do to you?

CarboN Monoxide. Fumes of the car contain carbon monoxide. This competes with oxygen producing hypoxemia causing headaches, nausea, dizziness, cardiac ischemia and arrhytmias, loss of consciousness and death. Never start a car with the garage door closed. Any headache inside of an (old)car may be related to scapes of carbon monoxide into the cabin.
Try not inhale them. Petroleum byproducts could not be good for the lungs. Check out the pollution stats in your area and avoid the fumes.