well i've been having a problem with getting my idle to stay steady, it'll bounce from 450rpm-1200rpm. I've already clean out the iacv and even replaced it with a new one. There are no vacuums leaks either. So im clueless. Anyone have an idea of whats going on? its driving me insane!. I've also tried adjusting the screw on the throttle body but that doesn't do much. My setup is t3/t4 odb1 ecu on a 99si

 

While this oscillation is happening, unplug your IACV. What happens?

What should happen is that your idle should drop to about 500rpms and remain stable. If yours drops, but is higher than this, use the idle screw to lower it back down to 500rpms. Turn your car off, plug the IACV back in, reset your ECU, and start her back up. Should be sitting at ~750rpms.

 

i did that and the car stalls. any more sugguestions?

btw thanks!

 

I had the same issues. Did every thing that you did, like 5 times. Turned out that it was the ECU. I swapped in another P75 and the flucuating went away. I am not saying that this is your problem, just telling you how I got rid of my issue. It was wierd because the ECU did everything else fine, so i did not think that it would be the problem, but it was. HTH


Rob

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rjardy &raquo;</TD></TR><TR><TD CLASS="quote">I had the same issues. Did every thing that you did, like 5 times. Turned out that it was the ECU. I swapped in another P75 and the flucuating went away. I am not saying that this is your problem, just telling you how I got rid of my issue. It was wierd because the ECU did everything else fine, so i did not think that it would be the problem, but it was. HTH


Rob</TD></TR></TABLE>

does anyone know if bad ecu's do this alot? if at all?

 

I'm putting my bets on the fast idle valve. If you search around that is a common culprit of poor idle characteristics...more so than the IACV.
I just installed a new fast idle valve to cure a hunting idle on my Civic and it cured it right away. Wish I would have tried it first before diving into searching for air leaks.

OH but you have a 1999 Si....I think the fast idle vavle was eliminated on those engines. Sorry that may not help then, but it may help someone searching for an answer later on.

 

So if it drops to 500 and remains stable this means the IACV is still good? I have the same problem on an '00 Integra. Eliminated all vacuum leaks, and when I pulled the IACV, it dropped to a stable 500. Cleaned it out, problem went away for about 3 days and then came back. It's only really bad in cold weather, when the weather warms up, the bad idle goes away most of the time.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EE_Chris &raquo;</TD></TR><TR><TD CLASS="quote">While this oscillation is happening, unplug your IACV. What happens?

What should happen is that your idle should drop to about 500rpms and remain stable. If yours drops, but is higher than this, use the idle screw to lower it back down to 500rpms. Turn your car off, plug the IACV back in, reset your ECU, and start her back up. Should be sitting at ~750rpms.</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by igotyofire &raquo;</TD></TR><TR><TD CLASS="quote">

does anyone know if bad ecu's do this alot? if at all?</TD></TR></TABLE>

uhmmm I DO!!
I replaced everything in the idle circuit, and it fixed nothing, swapped ecus and it fixed.


Rob

 

Another quick question on this topic.

Every time I try something to fix the problem, it goes away for a day or two and then comes back. What could be causing that?

Fixed the vacuum leak at the intake manifold gasket, problem went away for 3 days and then it came back.

Cleaned and inspected the IACV valve, car idled perfectly for about 2 days and then the problem came back.

Just adjusted the idle screw, fluctuation went away immediately for the rest of the day, and the next day it came back.

I'm totally out of ideas here. I guess the ECU is the only thing I havent' checked, but I really don't think it's the problem. The car is a '00 and only has 39K on it. Everything runs fine, the car just won't idle. Keep getting the CEL code for the IAC, but I'm thinking that's just the symptom.

This problem happened a few times before the turbo install, but after the turbo, it's a constant thing, especially now in the winter time. Cold weather makes the problem so much worse.