I haven't run the 'stang for about 10 or 11 days because of snow but the roads are nice and clear so I took it to work today. Was just sitting in it with it idling in neutral, engine warm, while stuck waiting for a train and I noticed it was idling back and forth between about 600 and 750 rpms which doesn't seem terribly out of the ordinary but then it would drop to about 500 and nearly shutoff, catch itself and ramp back up to 750, go back to close to 500 again and then eventually just do the 600 to 750 thing again. It'll then run smooth for a while with little to no fluctuation;however, when I got back to work I let it idle for a minute and it repeated the whole process. Any ideas? It runs fine otherwise. The weather has been in the teens at night the past few days so I'm thinking maybe the gas in the tank isn't any good anymore but perhaps one of you has a better idea of the issue.