after several attempts (and several hundred dollars) I am no closer to fixing the idle problem on my '91 DOHC ZC.
No, it is not doing the fluctuating idle thing (although it went through that annoying stage), but here is what's going on:
According to the manual, to set your idle speed, you do the following:

1) warm up the engine to normal operating temperature
2) disconnect the EACV (idle should drop a couple of hundred revs, check light comes on)
3) set idle speed (screw on throttle body) to 650 ±50 rpm
4) shut it off, reconnect EACV, re-set ECU (10A hazard fuse out for 10 seconds)
5) re-start, ecu automatically adjusts idle speed to spec (around 800-900 revs)

This all sounds great, but when I disconnect my EACV nothing happens. I have tried three different EACV's
with no change; the resistance of all of them (across the two pins) has been to spec; the voltage at the EACV
connector is within spec (about 12V). If, when disconnecting the EACV connector, I jiggle it in and out a bit,
the EACV clicks and the idle reacts, but that is about it. Cold starting is no problem, revs are between 1500-2000 rpm.
But when it warms, the idle stays at the disconnected EACV speed of 650±50. WTF?

I would like to swap out my ecu with another to check it, but PM7's are a little thin on the ground in my neck of
the woods. Has anybody had this problem? I have taken it to two different shops, and all they do is adjust the
idle screw to 800 rpm (and steal my wallet).

any info appreciated, as I am going out of my mind

thanks

 

Replace it; sounds like messed up iacv.

 

replacing the EACV was my first thought, but as I stated above I've tried three different
units; they all seem to check out OK, and at $50 a pop I am not sure how many I would like to try.
I could buy a new Honda unit at $250, but I would like to save this as my last resort. I guess what
I'm trying to say is that I think I have ruled out the actual EACV unit as the problem. Has anybody
heard of a second idle adjust screw on the throttle body???

thanks

 

u ever fix ur problem?