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[PLANETNZ]

HI Guys, quick qestion, how does the idle control valve actually work? i imagine that when you put your foot down off idle the ic valve closes so the engine operation is controlled by the main multiram valves?  is it also just a 12v feed to the solenoid, to check if its working.

the reason im asking is that my car has an ass of a misfire and I hear a constant hissing from the icv valve, presumably its open all the time. even when accelerating. i have a feeling that my coil -DIS  is stuffed causing the misfire but im trying to get to the bottom of this icv noise. cheers!

[Andy H]

Not sure of my facts here but I think the IACV comprises a rotary valve turned by an electric motor (but it might have a rotary electric solenoid with a spring return).

I think that the ECU only adjusts the IACV when the throttle position sensors reports that the throttle is closed. When you open the throttle the IACV should stay put until the throttle shuts. Not sure what happens on overrun.

First thing you need to check is whether the hissing is due to the IACV working normally or whether it is an air leak letting unmetered air into the inlet manifold.

[PLANETNZ]

Cheers im working on it now!,
The reason I am realy chassing this subject now and are looking for a few more ideas from you guys is that I have been reading a few OOF posts (over 200!) from other members who have had similar symptoms but there hasnt been a cause or fix except cleaning the ICV as part of normal maintenence so maybe its a bit more of an issue than first thought? Most members posts just take it as now being "normal". This problem also seems to coincide with higher MPG /loss of power. What i am thinking is that something, either a bad sensor or something is causing the ECU to keep the ICV to stay fully open at all times.

So with my car; Deduction. My car has had a few problems the past month, new cover gaskets leads plugs etc, still not running %100, still consistant rough idle and running, waiting for a new DIS. The "noise" is quite loud and can be heard from inside the car so obviously a high amount of air entering the intake..somewhere.  Slowly squeezing the intake hose from the multi rams to the ICV changes/ stops the noise keep squeezing and the engine stalls, so its a good guess this is the source. driving the car you can hear it from inside up to about 2000rpm so instead of this closing what would cause the ecu to keep the ICV open, this assuming its working correctly? Im asking this not only for the way my car is currently running but also from the other similar posts whos cars seem to be running fine?.

[Andy H]

The only reason for cleaning the IACV is to free it up when it gets gummed up with oil from blocked breathers. I don't know of anyone doing it to try and cure induction noise

I don't remember induction noise being audible when I had a 2.5 (unless I actually pulled the IACV away from the plenum to cause it to leak).

Poor running might be causing the ECU to open the IACV wide to maintain idle but I don't think it should make a lot of noise doing so

I still think you have an air leak (but this doesn't mean that there are no other issues to attend to).

[PLANETNZ]

hi, ICV is clean and working free it seems for some reason the ECU IS keeping it open at all times?! The noise isnt a leak its a full on induction noise that stops and will stall the car when you squeeze the icv pipe.  so my question is what sensor would the ecu be taking info from to be keeping the icv open...water temp sender / crank sender.  Actualy just thinking..would a crook crank sender cause a mildly rough idle and running, the car starts fine.

[Andy H]

My understanding is the the ECU will open the IACV as far as necessary to maintain idle. The fueling is then calculated from the mass air flow (with corrections for temperatures and lambda as appropriate).

Given the sudden big change in the way your engine runs I would start with the basics
- read the codes
- measure compression
- check the cam timing (to check that it hasn't jumped a tooth)
- etc etc

[PLANETNZ]

All sorted! the new coil finnaly arrived and now fitted, runs like a dream and the ICV noise has gone so working on that assumption it was the computer opening up the valve to compinsate for the bad running, interesting....

[cem_devecioglu]

All sorted! the new coil finnaly arrived and now fitted, runs like a dream and the ICV noise has gone so working on that assumption it was the computer opening up the valve to compinsate for the bad running, interesting....

ICVs are also wear tear items.. and an old one wont be healthy as a new.. if I were you, I would check my alternator components and battery condition also..
 
http://www.omegaowners.com/forum/index.php?topic=90619.0