my '93 prelude is calling for a code 23 (knock sensor). i was just wondering how important is this sensor and should i be in a rush to get a new one? what could happen if it is never replaced?

 

Whenever your ecu throws a code it will go into what is called Open Loop, meaning it's using pre-programmed info to run the engine, you may notice a decrease in gas mileage. Take your lude to your local mechanic or I can send you the flow chart to diagnose it ( you need a dvom/multi meter). I would get this diagnosed and fixed soon, if it's just the sensor its self or a wiring problem then no harm done to your engine, if you have tons of carbon build up, poor ignition system(resulting in a misfire) damage can be done. During detonation cylinder pressure can be up to %50 more than normal.