low'n slow

As the title states, I'm having a small idle issue. My car idles comfortably at 750rpm during the day, as soon as I turn my lights on at night there's a light surge at very low rpm and the engine nearly stalls. Stock head lights no HID's. It's pretty annoying /:

Vladglad

what year is the car and what model etc ?? moslty on civics what happens when you have a bad idle is the IACV =idler air control valve witch is lacted behind the intake manifold unscrew in and clean it out that migth help

low'n slow

93' coupe ex model, jdm b16a, sk2 IM, stock tb, (original engine harness, uncut)

Lol, I'm not exactly a noob, and if you read the post correctly it states the car idles comfortably at 750 daily. The engine only surges/idles low when the headlights are on.

TomCat39

Does it constantly fluctuate with the lights on or just initially when you turn them on then settle back out to steady idling?

If the latter, it's probably just like my rad fan in the summer, the initial draw zaps current from the system, idle drops, ecu compensates by surging engine a bit, then settles down to normal idle.

If it's doing it all the time the lights are on and never settling out, I'd suspect some sort of electrical problem (shudder). Me no likey electrical issues.

low'n slow

It's doesn't fluctuate at all/: when the lights are on the idle drops to just above 500rpm and lightly surges, when I turn my lights on idle goes back to 750 and stays there, comfortably.

I've been told it could be because a loss of coolant but the engine doesn't smoke, doesn't over heat. Brand new thermostat, IACV, coolant temp sensor, radiator.. It just doesn't make sense. Could it be a bad ground somewhere? I'm drawing a blank. ):

TomCat39

I probably would be looking at the alternator myself, could be getting old and not able to provide the full current, even though from what I understand the current draw of the complete system is no where near the max output of the alternator...

The other option is what you were mentioning, maybe a bad ground, hear it wreaks havoc on the electrical system. And old Honda's are known to have a couple of ground issues, like the one on the transmission to chassis.

low'n slow

I'm going to assume its a bad ground somewhere because the battery and alternator were replaced less then a month ago.