'90 civic surges at idle

I just put in a japanese imported, low mileage motors into my '90 civic. Everything works great, no more smoking problems. However, when we took it for a test run, we noticed that it surges while idling. You can definitely notice it, but it's not extremely huge. It did this before when we replaced our old motor's head gasket. All we did to fix it back then was plug the wires in the distributor more. We tried that this time, definitely didn't work.

It only surges when idling, not while driving, unless we put in the clutch long enough to notice it inbetween shifts.

Any suggestions would be greatly appreciated.

-Jadesh

Check your idle screw or eacv (if its dirty, clean it.). Try lifting the gas pedal w/ your foot. also there might be air bubbles inside your cooling system. I heard that also may cause a weird idle.

ya its is possible. when my car is low in prestone it does that!

It will do that.