I have an original US Air checklist from 1991 for the 146 and it required Engine A.I. to be selected ON (if not already on) after shutdown. The next mention of these switches is in the After Start checklist (OFF or ON as required) so the implication is that they remained on for the entire time when parked.
The current factory checklist says the much the same, but is more repetitive, just in case some well-intentioned but ill-informed engineer turns it off.