My car just started doing this last night. Last night I was driving home at night. Got gas my car tried to idle at like 400 rpm. I threw it in neutral and reved it up to save it from dying. Took my foot off the gas and the rpms fell that low again even in neutral. It did this 2 times last night. This morning it did something similar but not as low it dropped to around 600. Any ideas what the problem could be. IK with my lights on it strains the alternator but usually not that much. I am thinking vacuum leak, or pcv maybe. IAC? Any ideas? Comments? BTW my car has 135k miles on it and it is an automatic.