Suicide by carbon monoxide usually entails a hose from the muffler to a slightly open window or parking in an enclosed garage, windows down, car running for several hours. I don't think this was the case with the rag....
it almost really doesn't matter. Because the lead investigator on the case is actually the person to suggest the rag in the tailpipe as a possible suicide attempt which IMO likely means, he personally confronted fred about it, at a point in which Fred was in major regret mode that he ever even put in the mind of investigators that his daughter might be a danger to herself.
I personally think it's a silly way to try and end your life, but I don't believe its impossible.
Not just the Buckwild instance, but there have been may other innocent deaths caused by carbon monoxide poisoning.
I remember reading about a older gentleman who was scraping his windows during a snowstorm (and his exhaust was plugged with snow) and by the time he got his windows cleared off, his grand-daughter had passed away sitting in the car.
So it can happen, but in Maura's situation, she wouldn't have had time.
There is rumor (not proven) that she had one of her back seat windows cracked open, but I have not been able to confirm that as fact.
Plus it would really depend (in her situation) whether or not her car could start after her wreck.
Many cars will not start for a period of several minutes after a wreck (some safety mechanism),
However, one of the witnesses that night, believes Maura backed her car up after the wreck, so it's possible the car still started.
I don't know.