You can usually disable spark & fuel all together by pulling a fuse or 2, depending on your car. I don't have a wiring drawing for a '90 Civic, but that might be easier than unplugging injectors. (Unplugging the injectors would work.)

Incorrect valve lash can make clicking noises, but Honda fuel injectors are kinda loud, too. Leaking valve seals wouldn't make noise like that, would they??