I noticed when I have my headlights on, my car idles around 950 rpm, but when the lights are off the idle drops back to normal. I took it into the dealership and the tech adjusted the idle and said that the idle was off a bit. Well I'm back to square one . It still idles at 950 rpm when the headlights are on. Did anyone have this problem or does anyone have advice as to what I should do?

 

bump

 

maybe your timing is a little too advanced, see if that could help with your situation

 

That might be the problem. Thanks for the help, I will post if it works.

 

If the ignition timing is ok, then it may be the Electronic Load Detector (ELD) that is at fault. It's job is to warn the ECU when the battery voltage drops due to an electrical load. The ECU will then compensate by advancing the ignition timing and/or varying the idle air. It may also be the ECU at fault here. Try to get a similar car to swap the two parts out to see if the problem goes away.

Your honda should throw a MIL code 20 but this is only if the ECU does not get any response from the ELD at all.

The ELD for the prelude is located in the engine bay fuse box, I am not sure about other hondas.