The 'Second Generation' of Honda Preludes refers to the models marked with years 1983 thru 1997.
Common Problem Fixes
Fortunately, many of the problems you may encounter with your Honda Prelude have been encountered by others before. If you're having a common problem with you Prelude, chances are, it might be listed here.
Having an erratic idle is a problem that frequently shows up in 2nd Generation and 3rd Generation Preludes. The solution to this problem is often the same; you need to replace your IAC (idle air control) valve (sometimes referred to as the Fast Idle Valve). This valve is located on the side of your intake manifold closest to the engine compartment firewall. The valve is connected directly to the throttle body, as well as being connected to two coolant hoses.
To replace the valve, simply disconnect the coolant lines and unbolt the valve assembly from the intake manifold. Warning: do NOT disconnect the IAC valve until your engine is cold, if you do, the pressure in the coolant lines will spray and badly burn you. Once you've got the old valve off, do exactly the opposite and install the new part. After installation, it would be a good idea to purge any air out of your cooling system as some air would have been able to enter while you had the coolant lines undone.