Well I replaced my radiator on saturday after it blew and ever since then my civic been having a rough idle, I can still feel the engine shaking when I drive but it isn't as bad as when I'm waiting for a light. Anything I can do to calm down the vibration lol, any help would be appreciated. Btw, it's a 1997 Civic coupe DX, also the mechanic put in a jdm motor two weeks ago and I changed the spark plugs last week.

 

try running some of that seafoam stuff through the fuel system and see if that helps

 

I know that when an EGR valve is stuck open, you will have a really rough idle and at low RPMs. When you get to a little higher RPM, this will go away since the EGR valve is designed to be open. This is just one of many possible problems that could cause your rough idle.