civic idle loop affected by electrical load
 

my 1992 civic vx will sometimes have the idle loop, were it bounces from 700-800-ish rpm, up to 1,200 rpm then drop back down, I've searched for a vaccum leak and found nothing, I've even replaced a few hoses, and after owning a mid 80's civic with 56+ vaccum hoses I've gotten good at tracking down leaks, so something with about 7 hoses was so simple, now what I've noticed is that when I turn off electrical loads, the idle settles down to the proper slow idle, but lets say I turn the heater fan on, or the cd player while sitting at a stop light, it starts to bounce, is this an electrical imballence? where should I start looking for a problem?

I'll pretend to know what I'm taking about for a second. Don't take anything I say as gospel however.

I would check your IACV and your TPS sensor. Both of these control your idle.

what is the IACV?
I have a brand new TPS as of a little less then a year ago (don't ask how much they cost) it seems to be strickly electrical load, of course things like head lights bump up idle to make up for their load, but I don't think other things do, do they?

Idle Air Control Valve, on the back of the IM, one plug and two coolant hoses, two 12mm bolts. Also called EACV.

I forgot to mention, hondas have ELDs, eletrical load detectors, which change idle speed based on electrical demand on the alternator. I'm sure you'd notice if you started bumping two 12s in the back at idle, :p

Is it possible the ELDs have gone bad?

You'd be throwing a code usually. At least I've heard that in every case. It is a possibility, however. Unfortunately I have no idea how to check/replace the ELD.

I don't think the ELD alone could cause an idle to bounce like that. Most countries don't have them... it's mostly a US thing. Note that the manual says the 'check engine' light doesn't turn on due to ELD. You need to jumper the test plug to get the code. It only advises the check if the idle is too low.

The manual has a pretty simple check procedure: remove the 3-prong plug from the bottom of the ELD to check that it's got power and ground. Then plug that back in and check on the output if the voltage drops when you turn on the headlights. I think it's supposed to be analog and proportional to load.

It seems like a bad IACV could do it. If it's sticky, it could bounce the idle around. I'd pull that thing off and clean it out. It might fix it.

Hmm, I'd assumed the ecu could detect a bad eld becuase it'll do so in the case of missing one, Iono. i'd try IACV, I have a spare one if you want it.

If you're pinning it to electrical load, my bet is the iacv. try cleaning the screen or swapping in a new one. or you could try the troubleshooting guide in the HELM or the OBD training manuals.