You most likely need to replace you spark plugs. It is very possible that you need a tune up. If you are having this problem you may want to get a diagnostic test run and check the oxygen intake sensors.
First thing to check is the air filter the second is the pcv valve and the third is the fuel filter. If all of those check out ok then clean out the throttle body and pay close attention to the idle air control valve. Clean it out with brake cleaner and also clean the egr valve out too.
The Honda Prelude stalling while could be a multitude of problems none of which can be fixed by a amateur mechanic the best course of action will be to have a service an a registered Honda mechanic
Start with the basics. Perform a factory suggested maintainence on your vehicle. This may include spark plugs, wires, air filter, fuel filter and battery. Next check for vacuum leaks form hoses or the intake.
You have the idle set too low. You can manually adjust the idle on the prelude by letting it run and turning the "RPM RUN" switch with a flathead screwdriver. Ideally, you want it between 1500-2000.
First check to see if the throttle cable is lose. Most times to cable slides over time, thus at idle your throttle body shuts completely instead of staying barely open.
