90_civic_Si

Just to clear things up about testing your IACV. I read that while running your car at normal operation temp with your intake tube off you can plug the inlet hole of the valve and if the car shudders or dies(almost dies) that the valve is no good? Is this true?

I have had this idle problem for some time now and i did this test and the idle dropped to almost nothing the is died. So does this mean it no good.

frank_el_tanke

iTrader: (4)

you probably need to clean your iacv with some brake cleaner. that will help with your idling problems.

90_civic_Si

I have cleaned it and it's better but still not right. When i am coming to a stop and push the clutch pedal in the rpm drops to about 800 and then jumps back to 1300. Then when i fully stop at a light the tach goes down to 1250, 1200 and then maybe 1100rpm.

It's like something is not properly closing all the way. At a stop it just comes down in notches like, not just pushing the clutch pedal and rpm stays at a proper idle.

I have replaced, TB gasket, checked all vacuum hoses, changed coolant temp sensor, checked tps reading(.45v to 4.5v WOT). I have sprayed carb cleaner on pretty much everything under the hood and rpm does not jump. That's why I asked about the IACV, is it normal for it to stall and die or should it be replaced. I would just replace it but it's a kind of expensive valve to just throw in...

frank_el_tanke

iTrader: (4)

have u tried cleaning your fitv?

90_civic_Si

I don't have one.

frank_el_tanke

iTrader: (4)

maybe the idle screw needs adjustment... when i cleaned my iacv on my crx i had to open the idle screw because there wasn't enough air coming in.

frank_el_tanke

iTrader: (4)

what engine setup r u running?

90_civic_Si

I have a DOHC Zc that was already installed in the car when i bought it. The idle screw is all the way in and it still idles at 1200~1000rpm. It doesn't hunt between these ranges it's either at one or the other. Sometime when it's at 1200rpm at a stop light is will come down slow to 1000rpm. Sometime it's even as high as 1500rpm and will slowly come down to 1000. It driving me nuts and everything that i have read on fixes i have done.

I'm gonna try and find a good used IACV and see what it does.

McGruber

What is the normal idle supposed to be at? Also does the idle fluctuate if you turn your lights on or ac or anything like that?

90_civic_Si

It's probably suppose to be at 750~800rpm. The idle does go up when the cooling fan comes on but that's normal for most vehicles, it does go back down though. Even if my idle was at 1000rpm it would bother me. It's just that it's at 1500, 1200 and sometimes 1000rpm.

So what else would cause the idle to do this? It just doesn't come down smooth like it should when coming to a stop. It has to be the IACV. I gotta change it tomorrow and see if anything is different.

McGruber

I was just thinking that if your rpm's dropped all of a sudden when you turn on any accessories it might be the alternator or battery. But seems like your issue is the idle being way to high.

joshkrieger

where is the iacv at? some one told me to clean mine to smooth out the idle

el-loquito

I've been through this before and this was the only thing that fixed it:


I tried cleaning it, shaking it, soaking it, etc.
I got at least 3 of them used from junk yards and they all in one way or another were bad.
These valves wear out and need to be replaced with NEW ones.

90_civic_Si

*****Just and update for those who are searching and have the same problem. After swapping in many IACV's and changing all vacuum lines, throttle bodies, etc....

I swapped in a pm6 ecu and it started up perfect and had proper cold start idle and has been running perfect ever since!!! So if you have a DOHC Zc with the pm7 ecu and have weird or erratic idle problems just find a Si ecu FIRST before spending days and hours chasing this problem. It takes 5 minutes to swap in a ecu. I might have just had a bad ecu but who knows it looks fine.

CRXguy_88

iTrader: (7)

we i have a pm6 ecu and my idle bounces around. after running a bit.. what you think my problem is? sorry this thread is old haha

Nooch

Did you read all the suggestions already given throughout this post? Go through each and every one and test your vehicle. It will be at least a GREAT start for it. Come back with all information and what changed. Then reply if you get any codes thrown.

jlk16188

Mine does this sometimes too but it has nothing to do with any of the idle systems. I have a sohc zc swapped into my dx crx with a dx throttle body cable. The cable is too long but still works just fine. I had it run over my valve cover through the stock clips and holders and the cable was getting too hot sitting there and would stick in its casing. As soon as I took off the clips and let it sit wherever it wanted, all of my problems went away...

just a suggestion, a little out of the box though