2011 Civic engine vibration rpm fluctuating
 

2011 Civic LX with 64000 miles. When i start the car and engine is cold i can see the rpm fluctuate up and down about 30-40 rpm. Smooths out a little when the engine is warm, however, when i stop at a light, i can feel the steering wheel vibrate and you can feel the engine is not running smooth. I changed the spark plugs and air filter. I was going to use Seafoam, but i read its not good for newer cars. I don't know about it. Also read some stuff about bleeding the coolant maybe? Any tips?
No check engine light.

Thank you.

Re: 2011 Civic engine vibration rpm fluctuating
 

An internal combustion engine vibrates because of explosive action. More explosions per revolution, less vibration.
Electric cars vibrate much less when stopped.

Re: 2011 Civic engine vibration rpm fluctuating
 

I forgot to add, that i got a message on the dashboard to check the gas cap. Also, you can tell the car is little bit weaker.

Re: 2011 Civic engine vibration rpm fluctuating
 

Has a valve adjustment been performed? If so, when?