Maybe I should have posted this in 92-95 but starting here.

Idle is dead on and steady during daylight hours, but when the headlights etc. come on I'm getting a bouncy idle between 750-1500. Turn lights off and it stops. Think this is the Electric Load Detector (ELD)? I have never had to mess with one of those in the 23 years of owning an EF. I did just install a reman Denso alt in hopes of correcting this but no luck.

 

LINK: https://honda-tech.com/forums/honda-civic-del-sol-1992-2000-1/bad-eld-2663262/

Our cars throw a CEL 20 (OBD0) I believe for bad ELD. Or out of spec electric load. That thread does say to check the grounds. You could just be running into corrosion on the grounds. Check your negative battery terminal, thermostat housing ground, transmission ground and valve cover ground. Then, check the ECU D16 or wherever the ELD is wired into. It may have come loose or something. I'm not familiar with this specific swap. (SOHC VTEC?)

Maybe someone with more experience will chime in.

 

Most of the time defective alternator brushes cause this type of problem. The brushes are not clocked correctly and jump, which as load is applied will cause arcing across the rotor field, causing a bouncing idle.

In a few cases, a severely damaged battery can emulate some of these problems. As a preventive measure, ensure all of the grounds required of the vehicle exist, and are in good condition.

The fact you have a bouncing idle proves the ELD is working, as it attempts to spin the engine, and thus, the alternator, faster to keep up with the load on the electrical system. The poor brush contact reduces the current produced, then the ELD commands the engine to idle faster because of this poor contact. When it makes good contact, the idle is reduced, voila! Bouncing idle.

 

Thanks guys for your replies. I will double check all grounds. I did this swap little over a year ago, and have had these symptoms pretty much since but may have been there before, can't really remember. I did go from OBD0 to OBD1 with a custom harness so my wiring should be good. I installed new battery in the last 3 months and the new alternator just last week with no change in the idle. I would agree the ELD does seem to be working since the idle does change when a load is detected, but wasn't familiar with the entire aspect of the ELD and since Honda bouncing idles are so common when you search you get a million posts, mostly on non ELD topics. Thanks!