Rough idle in gear

[rickfen]

I have approx. 40k miles on a 3.8 sedan. Once the car is completely warmed up, I've noticed a slight "surging", "seat thump", (not sure how to describe the feeling - I can feel it through the seat), when I stop at a light with the car in gear. If I put the car in neutral, the "thump" goes away immediately. I would say the idle is "lumpy" but only if the car is in gear with the brakes on. It's not a brake issue, it's definitely to do with the "tuning" of the car.
It's not a big "thump", but enough that it indicates to me that something is not quite right.

Any ideas, here

thanks

 

[WowCool]

If you feel it's wrong - pop along - to your "H" dealer.. Take the tech out for a spin & go from there..Sounds like tick-over is a little too high...
When was it last serviced? have you changed to a different fuel? how about running with everything On (a/c,lights,etc.etc) do you still get the thump?
It could be a Tranny issue - everything is electronically controlled..

 

[homeofstone]

Have the filters been changed? Air, fuel tank Air filter, fuel filter

 

[Vermillion3]

Do you feel it in the steering wheel at all? Does the wheel shake any? Is there a noticeable difference in power train sound from when she is in D or R as compared to N or P? My guess would be motor/trans mounts. The reason why I say this is that in addition to all of the above mentioned I also felt what could only be described as rough idle and shaking in my drivers seat. After much fighting with several dealerships one finally R&Red the mounts and wouldn't you know it rough idle was gone too. Is your Genny a 2010 or 2009 these seem to be the ones more prone to the bad mounts.