I have a 1990 Prelude Si (b21a1). I had some headwork done to the motor. It was ported, polished, 3 angle valve job, cams, and cam gears, as weel as a lightened flywheel clutchmasters clutch, and full exhaustand a MSD Ignition. The car runs high due to the new cams, idles around 1500. The main problem I have is when I turn on the lights, or turn the radio up, or the fans come on, or the AC, the idle drops down to like 500-600, and the car doesn't run right at that RPM. I am still running a stock ECU, so I am thinking maybe that is it. Then again maybe it is the alternator, maybe I should use a high amp one because anything electrical messes up the idle. Any help will be a big help so please post back. Thank you.

 

all that work done and the
ecu still stock..
is like doing nothing to your car.
so why bother doing it...
so first step upgrade your ecu and play with your
idle control valve after you are done.
but as the car is now
you find yourself charging the battery often..
right!!!

 

I don't know of any company that makes an ECU for my car. The only company I know is JET that can upgrade my ECU. You think that is worth it, for the 250 bucks? I know I have to upgrade that ECU, but I don't have many options. Thank you for the post though. Do you think the alternator even matters, I took a reading on it, and I know it works, but I am not sure if it has enough amps. Leave me another post. Thanks again.