Hello Civic pros and lovers of the civic...

My uncle purchased a used 2004 Civic 4 dr ex with 236k miles.
Car broke down driving to Orlando and what I was told was that the radiator was replaced as well as the head gasket.

Since that was done to the engine, when starting the car, engine vibrates with a steady idle of 900 rpms. Now if I move it from Park and put it in DRIVE or REVERSE... it hesitates. When I'm at a stop light with the A/C on... the vibration is the same. But when I turn off the A/C off... the vibration stops. It's really confusing for me because I've.read that I needed to change the spark plugs (which I did) and it's still the same.

I've thought of engine mounts needing to be replaced or adjusting the idle?

I really dont know. But I'm glad there are sites like this for us!

Thank you in advance!

Any help will be GREATLY APPRECIATED!