Hey guys I have a idle issue with my 90 crx. It has a zc sohc in it (d16a6) with the hf intake on it. (I bought it that way)
Anyway, I was having idle issues so I looked through this board and read about cleaning the IACV. Well at first I could not get the hoses off of it and just cleaned the screen with cleaner and let it dry out (the screen was dirty). Put it back on and there was some improvement but not much.
Then I bled the coolant line and that helped quite a bit but I still could not get my idle down from 1-1.5k
So when I had more time (and the right tools) I was able to get the lines off and properly clean the IACV. I also took apart the back plate and it was really dirty. filled it with cleaner and let it dry, hooked everything back up and it idled properly.
Well after 2 days of driving the idle is back up to 1-1.5k. So I took it off again cleaned it and now it idles properly. I have not driven it again yet, but I am really thinking that it is going to do the same thing again.
Is there something I am not doing? I have followed the cleaning steps to the "T" and am starting to think something else is the issue.
Now this time I have made sure the coolant bottle is filled and the coolant line is bled.
I do not have a FITV so that is not the issue.
Is it possible that my IACV is bad and needs to be replaced. I really do not want to spend 200.00 on one.
I am quite shocked at the price of Honda IACV's I have always known all the other IACV's on cars that I have worked on to be around 40.00.
Any suggestions?

 

I just replaced my IACV, and the second one I put on was bad. Third one was the charm. Go to a junk yard - they had 8 IACV's when I went last weekend, and they were $7 each.

Check the resistance of the winding - it should be in the 11.5 ohm range.

With the car running, unplug the IACV - your idle should stabilize (if it lopes) or bog down (if it is high). If it doesn't, the spring is too weak, and you will need to replace the IACV.

When I was looking for IACV's this weekend, some had screens and some didn't. I bought one of each and am using the one without the screen.

The coolant supplied to the IACV is only there to prevent it from icing during operation in a cold environment. The temperature increase from the coolant does not affect the IACV's operation in any other way.

You might also look at replacing the rubber gasket. These are typically original equipment, and are flat and brittle. I have seen them be the root cause of idle issues.

 

I unplugged the IACV and I get nothing. This time is idled right for about 5 minutes and now it is back up. I am thinking I am going to have to get me a new one. I live in a small town and the salvage yard I usually get my stuff does not carry allot of honda parts, Seems like all the tuners have snatched them up before me.
This high idle just bugs me. I am thinking its going to have to be replaced. cleaning is not working anymore. Anyone else have any suggestions?

 

A high idle can also be caused by a vacuum leak. Actually, the IACV malfunction creates a vacuum leak.

Look in other areas for the vacuum leak.

Another way to check the IACV - (I have a DPFI, which is a little different than the HF manifold you have) for the HF manifold, take the intake off the throttle body and find the hole that feeds the IACV - it will be right by the throttle plate. Put your finger over it - does your idle fix itself? If it does, the IACV is your problem.

 

Going to try that in a bit,
I and another person have gone over all the lines looking for leaks but everything seems fine. Will check again though...
Check this out. I can put my foot under the gas pedal and lower the idle, but when I accelerate and stop again it goes back to 1.5k rpms

 

Yeah the IACV is the problem, Put my finger over the hole and the idle dropped to proper idle speed. Looks like I will be shopping around for one. I have cleaned this thing 2xs in the past 4 days.
Curious, if your getting them for 7.00 a piece, chances you might be in the DFW area?
Going to have to do some calling tomorrow to find one. Hopefully for 7.00
I REFUSE to pay for a 200.00 IACV that is not even made by Denso.

 

what exactly is the problem? you just have a high, but stable idle?

have you tried adjusting the idle screw? its over the throttle body.

 

well it ranges from 1-1.75k rpms. Sometimes its stable and sometimes it fluctuates.
I pulled it off cleaned it and it ran great at 800rpms after about 1 day running the idle went back up to 1-1.75k
Cleaned it again thinking that I did not do a good job the first time and its doing it again except it took less time to get back up to 1.75. almost 5 minutes.
I do not have any vacuum line leaks.
I unplug the IACV and nothing happens.

Also too here in Texas we just had a 80degree heat wave here and It seem to get worse with the outside temp.
Now that its cooler outside the car is getting closer to 800rpms at idle.

 

I have the same ZC motor as you do. today mine started doing the same thing. it always idled high but stable until the car warmed up. now it fluctuates like crazy even when i drop it in nuetral n cruise. i guess i'm going to try cleaning and/or replacing my aicv too. i hope thats the fix. (sorry that my reply didnt help you at all lol)

 

does it seem to depend on pressing the brake? like at a stop?

im wondering if your booster is bad.

http://www.norcalcrx.org/tyson/pics/braketest.jpg

 

if the iacv was bad wouldnt he get a code 14, i did when mine wwnt bad, id try fooling with the idle screw mine was on top in the center

 

IACVs can go bad and not throw any code. There was another thread on this:

http://crxcommunity.com/viewtopic.php?t=1354

Also I had this same problem and this is what I did to fix it. I cleaned the IACV numerous times. Went through many cans of brake cleaner. It would fix it then like 50 miles down the road it would start again. I bled the coolant, I cleaned the coolant lines going to the IACV I tried everything in every thread. It did not work. I even bought a brand new IACV from Rockauto.com for 179 bucks.No difference.

Ohh and to save you some money remember there is no difference between an Si and a HF IACV. The DX is different though, I think only in the coolant plate that goes onto it, but that can be swapped out. Also the differences in the 88-89 and 90-91 IACVs is that the older ones didn't have the little screen. Honda probably got wise to the fact that these get dirty and clogged and incorporated it into the later years.

So finally I gave up and took it to a trusted mechanic. he told me that someone who owned the car before me had adjusted the base idle screw. You never want to move this screw from the stock position. He adjusted it and now I no longer have any bouncy idle issues.

The screw I am talking about is below the TB if you are looking straight at it. With the car off move the Throttle cable and you will see that there is a little screw on the bottom that it hits when it almost closes the throttle. If this is set too high the IACV will be given all kinds of crazy commands by the ECU to open and close. The ecu is actually trying to correct the problem to its best ability. You can even see this if you take off the IACV and block off the two ports with scotch tape. Then start the car and let it get warmed up. You will need to hold the gas pedal because this is what the IACV does when you start up the car. It holds the throttle to warm up the car. Now look at the IACV and if you have idle issues you will notice it because the IACV will be opening and closing like crazy.

I would suggest saving yourself some serious headaches and just going and getting the following things done at a trusted mechanic:

Set the BASE idle
Set the Timing
and set the Idle adjustment screw. This one is on top of the TB.
And check the TPS. sometimes these go out.

Of course if you know how to do this yourself then great do it yourself. But if you are not sure go get it done professionally. It took me a year of tinkering to finally take it to a mechanic and get it done right.

 

Hey, Thanks for the help, I am planning on taking the car to a possessional who is going to adjust the valves, properly set the timing and as well adjust the idle properly for me. he charges allot but I know he will fix it right. I am just trying to see if I can fix it before he does without spending a few $100.00!
But things are super busy for me right this moment when things slow down I will take it to the right people. I know the owner before me did do some messing around with the adjustments because the timing is advanced somewhat not to mention the car having the wrong plugs and plug wires in it. (which helped allot with the idle, it was worse)
I know where the idle adjustment screw is, I just have not wanted to mess with it. I one time messed with the idle on an older toyota I had and from then on it never ran right.
Thanks for the tips, seems like this problem could be all kinds of things.

 

i have a 90 hf with the same motor and stock hf intake and same problem. I just bought the car cheap and the kid said its been doing this since the motor swap. so i took the one on the hf and used a used one off an SI i have in the barn thats been sitting for years so not to sure if its good or not. ne-way still same problem start car idles around 3000 rpm then tap the gas alil then it goes down to 1000 and bounces up and down from 1000 rpm to 1800 or so UP AND DOWN UP AND DOWN. HAs the code for IACV- drives pretty good when going down the road but when it warms up the idle get worse and runs like ***?????? ITS DRIVING ME NUTZ..HELP

 

Well, I will say to check your vacuum lines I found a small hole in one when I looked over it again.
I am not having the same issues that you are having. I am only having problems with it idling at 1-1.75 tops.
The guy who put the engine in Also put in a cruise control which he later removed. And I KNOW he had to adjust the linkage to the engine. I have been adjusting the throttle linkage screws and noticing a difference. I did not have allot of time to mess with it but the linkage seems to be where it might be. I can bring the car down to almost 500 if I loosen the linkage down.

Have you cleaned you IACV? Check that out first, Check what kind of plugs and wires you have. Also make sure the coolant is full (including the bottle) and try to bleed the line if it is.
The best results I got was by putting the NGK V power plugs with NGK wires (That makes a difference) as well as bleeding the line.
Also too, check your timing and valve clearance. If you do not know how to do it take it to a professional.
Right now at the most the car will idle from a cold start up to 1.75 but when it warms up I usually hover around 1-1.25 I can drive it fine like that but know that its better idling at 800rpms. It also uses less fuel that way.

I am thinking my problem is in the linkage. Anyone heard of linkage getting dirty? I know everything else under the hood is, so I guess it can be an option...

 

the bouncing idle, from 500-1500 and back again problem means you have a leak also. theres too much air going into the combustion chamber that the iacv cannot deal with so it goes into an open loop.

if you follow the helms, it will tell you to mess with the connector to the iacv and unplug the hazard fuse to clear the ecu...

however, i found that its just best to just adjust the idle screw all the way down, then slowly raise it back up. it always fixes it for me and takes a minute to do. the procedure in the helms never netted me any progress.

good to hear you found the hole jzak.