This is a multi-part question, tali, and needs a few clarifications, explanatiuons and 'putting in contexts'.
Exhaust is not all carbon monoxide. Carbon monoxide (CO) occurs as a result of incomplete combustion.
When you burn a fuel (usually a hydrocarbon), in sufficient oxygen (or at least air containing oxygen), the products are carbon dioxide and water. So, in theory, that's all you get in exhaust 'fumes'. In practice, you get a mixture of combustion products (CO2 & water), unburnt fuel, and carbon monoxide (CO).
So, is carbon monoxide gas poisonous? Well, yes and no. It's mere presence will not kill you like, say, hydrogen cyanide would. However, carbon monoxide (CO) binds chemically with your red blood cells, preventing them from taking up oxygen, so you eventually die of suffocation. (That's why it is the "silent killer")
So what about the rest of the combustion products? Well, CO2 is part of the whole debate about global warming as a combustion product. But per se, is not poisonous - (it is the gas in fizzy drinks after all).
Which leaves "unburnt fuel" - this is emitted in exhaust fumes like everything else. What does this consist of?
Well, unburnt 'petrol' (a mixture of alkanes in the C7 to C9 range) and? Additives.
Many and various chemicals are added to make the fuel "behave" - no matter how young you are, you will have heard of "unleaded petrol". This is because previously, a lead compound was added to petrol to prevent (let's call it) "premature ignition".
The combination of unburnt petrol, (including additives) combine with the other combustion products, such as water, to form "particulates". These are possibly the biggest (unquantified) long-term risk to health.......
[cont.]