The 89 Civic will have a cable-actuated throttle. You can probably put a lock on it up inside the dash, or in the engine bay where the cable comes through the firewall. You should be able to run a push-pull type cable (e.g., bicycle shifter cable) from the lock to somewhere reachable inside the cabin.
An even lower-tech lock was installed by Basjoos in his Civic. He built a hand throttle with a linkage (a stick!!) that went to the throttle pedal. The combined setup had enough friction in it that it would stay in place once applied. The major downside is that it was very obvious, which I know would put off a lot of people.
-soD
|