My 1985 Toyota Tercel, 1.5 liter 4 cyl, carburetor, surges when the throttle is held steady at about 1200 rpm. It starts well and runs well at other speeds. No smoke or backfire. New plugs and cap, clean egr valve.

Check/replace the Ignition Control Module (igniter). Autozone and O'Reilly Auto Parts will test for free. I'd have them check the coil, while you are at it, but I suspect the problem is with the igniter.