2008 Honda Civic 73,000 miles. When I start my car it idles rough in park and neutral, when I go in reverse it's just as rough. Just started happening in October, and I'm attributing it to it being cold. When I am in the accelerator and let off it has this groany congested throaty noise to it and is a little rough. I went ahead and got an oil change and put some fuel injector cleaner in it and it hasn't changed it. I'm thinking transmission, but I hope not, it's not old enough for tranny problems yet. I got a transmission flush at 38,000 miles. Get oil changes every time it hits 20% and have maintained it very well. When it warms up, the throaty noise goes away. Should I be concerned?

 

Idling poorly wouldn't be caused by the transmission. The transmission isn't doing anything when you sit still in park or neutral.

You should check for exhaust leaks as well as intake leaks. They make a putting or purring noise.