Hey guys i have been battling this car over the past week from fixing the head gasket then ignition coil that gave up the ghost. Now with those problems fixed no i have this, Once the engine is warmed up and is put into P or N the idle will bounce and surge up and down in RPM. When the car is in gear its perfectly smooth. Its an 1994 Civic DX Automatic. I dont thinks its a vac leak because it would run like crap when started cold it has me confused

 

reading the other posts here and i might try bleeding the air out of the coolent saturday and see if that helps great site i am a new honda owner my pops gave me this basketcase for free so i cant complain lol

 

bleeding seemed to do the trick

 

Yea its most likely from when you changed the headgasket and put more coolant in your car. Air will get trapped in the coolant sometimes.