I've done my best to read through all the different IACV in the different forums but still can't seem to figure what my problems:

Car: 1999 Civic EK hatch D16y7 Manual
Symptoms:
When bad - happens intermittently, not related to timing or temp or warm up: slight rough, higher idle, doesn't stall. when you put light load (throttle), the car rpms will more significantly bounce up and down, very rough. Then after a certain point, it will just surge. also notable jerk when coming off and on throttle.
When good - no surge problem, only thing I notice is that the idle bounces a bit after a load until it settles

Diagnostics: bought care with new aftermarket IACV. I went ahead and cleaned the IACV as much as possible and throttle body. No change
- when I plug the throttle body on firewall side: no change (no vacuum leak?)
- plug TB hole on IACV side: fixed. only been able to do when car is good and only having the bouncing idle until it settles but that does go away.
- unplug IACV: again only able to try when car was good. when I unplugged it, it seemed to bring about the problem that I'm having. high rough idle. surge/rough throttle. again plugging the TB on IACV side seems to fix it.

From what I can tell, it seems my IACV is the problem. it is a new aftermarket one so not sure what the deal with it is. is the IACV supposed to close completely? I've attached a picture of it.

any help/thought appreciated.

 

Last month I had to replace the coolant temp sensor on my 93 del sol si D16z6. It's OBD 1 but the symptons sound similar. Your engine surges when it gets enough throttle and timing to handle the extra fuel it's getting. At idle the engine is getting too much fuel and it stumbles. Check your plugs if they are wet or appear to be running rich, ie more grey in color than tannish white they are running too rich. That's a hint.

 

you know with that iacv the two screws that are on the right on the picture
if you take them off and you tighted that big plastic screw inside all the way down
it will really help
just make sure that when you turning it back in only turn it till it stops turning
DO NOT TIGHTEN IT HARD just turn till it stops turning and 8/10 times that will fix your problem

by tightening that plastic screw you will manually close it that way the car will run like it does when you have your finger covering the hole
but now no finger nessesary ^_-

 

thanks for the help. I ended up ordering a replacement. Seems most aftermarket IACV have just one part number but higher end ones have one for AT and one for MT. problem fixed now.

great idea with the tightening, guess I could've done that instead of spending the $$

 

I've never heard of a plastic screw in an IACV. Is it possible you are confusing the FITV's wax screw with the IACV? If not, looks like i have some hunting to do

 

if this is a 96+ engine it will not have a fast idle valve in the 97+ models the iacv has a built in one that cant really be adjusted. having the same problem with my 97 dx