On my 89 lude I've got a crazy idle now. It will be about 2000 when you start it up cold and after warm up it'll do the 1200-2000 up and down surge.
This started after I replaced the v/c gasket (including valve adjustment and gapping plugs at .040) and bypassed the intake hoses like prelude3g.com recommends. I've double and tripple checked the valve specs. Int: .004, Exh: .007. Only thing I can think of is I had to remove the IACV to do the hoses and it's still got coolant lines to it.
Since this I've removed the FMIC and IACV and cleaned them both but still has the horrible idle surge. Most people say theirs surges til warm up where mine just idles super high until warm up then surges. I'm curious if anyone's seen actual BAD IACV's? And why would it go bad after taking it off unless the gasket behind it is causing issues? Spraying carb spray behind it doesnt seem to change anything but when it's surging it's hard to tell lol

 

what is your base idle set at?

 

No idea how to check. It was idling around 900-1000 before I started all this. I went out and played with the idle screw a bit. I can get the idle to go to 1000-1500 and from time to time it'll stay at 1100 but then start surging again.

 

Since im off today i'm tinkering with it off and on. I realized the lower half of the t-body was cleaned by the previous owner but the top half was gummed up. After cleaning it she idled great about 1200 for about 10 seconds then went to surging. If i sprayed the intake cleaner through it and cracked the throttle open once it clears out all the cleaner it idles great for a while then goes back to the crazy idle again. Also the head sounds like it's about to explode even tho the valves are adjusted to spec. I wonder if that's got something to do with it. Before adjusting it the intakes had about .010" and exhaust had .003" and it ran fine with very light ticking.

 

You have an intake manifold leak.

 

Im starting to think the iacv gasket is leaking. Its rock hard. I got the idle better. I sprayed intake with cleaner and after 5 mins of doing the 2000rpm spraying cleaner i got aggrivated and let the car sit. 30 mins later the idle stabalized at 1000. Maybe the cleaner got to the iacv. Think if i replace its gasket ill be good to go again.