My 97 Prelude been having issues with the idle dropping down and the engine gets rough from it going down so low. Sometimes it drops enough to cause it to stall out which can be dangous if your coasting off the freeway (no power steering and music going and u dont notice right away lol). Also note the problem only happens once the engine is warmed up.

The honda dealer i taken it to cleaned the idle valve, checked just about everything including the battery and alt (all checked out fine). This last time they ended up calling some tech line and told them to run the car with the computer scan tool ( shouldnt they have done this the first time??) they used plugged in and ended up doing a compression test saying cyl #4 is down @ 100psi (others r 125-130psi), suspect a slight bent on exhaust valve and want to do a leak down test to conform. My question is can a 25-30psi drop in a cyl. cause a idle to drop but only once in awhile? They also went on to note that the fuel trim (not sure what that is) was quite rich at .86 (1.00 is normal) but went back to normal on same test drive. Would that be anything? Only reason i ask on this forum is after being to the dealer 3 times it seems they are not sure what the problem is, which i can understand its not a problem that can easly be reproduced to check out. I done some research and the two top suggestions i seem to see for this kind of idle problems are to clean the idle air control vavle or replace the throttle position senser. If anyone has any other suggest or experiance with this same problem please let me know.