It's iffy. Yes, some have been successful using small engines in vehicles, even 4 stroke engines. There was even a movie made about one such instance called Conrad and Michelle. The thing about engines is that you'd be breathing in a lot more than just the CO, the kind of nasty stuff that would give you enormous headaches and other unwanted symptoms. Pure CO at a very high level, like 10000 PPM or more, should render you unconscious within a few breaths. Then you wouldn't be aware of any of the other affects that occur leading up to death. Ideally, you would want a way to measure the amount of CO within your "space" to make sure that the level is above the 10000 PPM threshold. That takes a CO analyzer capable of measuring a concentration that high, costing about $400 US, maybe a little less. But, people have just winged it and have succeeded, too. I guess it depends on your level of comfort. The consequences for failure are quite high. If you survive you could be left a "vegetable", unable to do anything for yourself, henceforth. That would include not being able to ever again take any measures to remove yourself from this new hell you might find yourself in. I'm not trying to scare you or anything. You need to make up your own mind as to what you want to do. I just think you should have all the facts while you thoughtfully contemplate any plan you might have.