Interesting IAC tid-bit

Post by **Legacy777** » Thu Jun 19, 2003 2:05 pm

Well after a year of weird issues and problems caused by cleaning of the TB, and changing certain things I've come across a pretty interesting little coincidence.

During my quest to get rid of the high idle, I changed the gasket for the IAC valve, thinking that may be the problem. That didn't help. I swapped a couple things, until I figured out it was the TB.

Well ever since I had all those issues, I had a high pitch squeal coming from some where in the engine bay under a certain throttle position. I tracked it down to the IAC valve, but couldn't figure out what the hell was going on. I tried swapping gasket to one that I modified, since the new ones were different. No luck. I tried swapping IAC valves back to the original one. No go. I had pretty much given up, when I decided to take a step back and look at things. What is different now then when I didn't have the noise. The only thing mechanically different was the IAC valve gasket. Lightbulb is sort of on, I didn't see how gasket would change things, but I figured what the hell, so I decided to put the old one back on. Good advocation for keeping all your old parts. Well guess what, I have no more squealing/noise!! None what-so-ever!!

The gaskets are of two different types. The original was a thin metal gasket with a compression portion that sealed things. The new one was a composite type gasket with metal core and what looked to be a graphite matiing surface. The two gaskets had their differences, but the main difference was thickness. The new one was at least twice as thick if not slightly more then the original one.

The only thing I can think of is some resonant frequency or harmonics were causing the noise. It's just amazing how changing a gasket thickness by the smallest amount can affect things.

Operationally, I think the car idles a tad better, but I couldn't say for sure.

Mark Ward is having this same issue. After swapping my old gasket back on, I suggested he try and find something to replace the composite gasket that's on there with a thinner one. If his squealing goes away too, I think we've definitely found an issue Subaru didn't forsee when superceeding gaskets.

ciper · Post by **ciper** » Thu Jun 19, 2003 7:08 pm

Im sorry I didnt follow your high idle thread closely. Id like to help now.

The reason I think I can help is that I had to smog one of my legacy and being a worry wort I connected a tach and found the idle to be out of spec.

It was pretty hard to get the thing to idle correctly. Raising the RPM to 2500 for 5 seconds and letting go or quickly blipping the throttle would produce different idle RPM. Also the cooling fans really through the idle off so you have to wait until they stop.

I finally had to get it in a range that would fall in the +-50 from either setup. I did get it to sit between 700 and 800 though.

What exactly happens with your high idle? Is it just always high? To adjust it on mine it was a combination of the IAC top and the bypass screw.

Post by **Legacy777** » Thu Jun 19, 2003 7:59 pm

My high idle issues are pretty much fixed. I have done some swapping back and forth of throttle bodies. What I've ended up with was the TB that did not have the bypass screw on it. (which is not my orig TB) The current one still has the black goo on it.

The IAC valve is the original one, with now the original gasket.

My idle is still kind of lopey. Cooling fans will piss it off slightly, and the a/c drives things nutty. When the a/c is on, and driving, when I come to a stop idle will come down and then blip back up to 1100 or so, and then slowly settle. It's become habit to simply take the car out of gear when at a stop light so the damn idle doesn't piss me off.

This behaivor seemed the same even with another IAC valve on there. I don't know if it is just an issue with my car, or what.

I do think I have some fuel injector issues, possibly a small vacuum leak..maybe not, and a charging system that could use a boost.

I'm planning on tending to the fuel injector issues and some other stuff once I move. Which I think will help things. I also need to get a new alternator, preferably a HO one.

entirelyturbo · Post by **entirelyturbo** » Fri Jun 20, 2003 4:34 pm

I have a new IAC valve with the new style gasket on my car, and have heard nothing strange from it.

My idle is still a bit weird at stoplights. It will drop to about 500-600 sometimes. Occasionally, the whole engine will shake very rhythmically like a motor mount is loose or something

.

However, once I turn my a/c on, it sits pretty at 850 rpm and idles as smooth as a new car and doesn't shake or anything. That tells me that the IAC valve is functioning properly.

However, I will admit my stupidity. Long ago, when I first got the car, I played around with the TB stopscrew, the one you're not supposed to touch. I ended up tightening it so much that I broke the head off of it

. I know far better than to do something like that now, but that broken stopscrew is still there, unmovable and way out-of-spec. I know that the ECU will adjust the IAC valve's duty cycle to compensate for something like that, so it's not like I've had a 2000rpm idle this whole time

. But I'm curious if this is causing my problem.

ciper · Post by **ciper** » Fri Jun 20, 2003 6:36 pm

Have you readjusted the idle switch?

Post by **Legacy777** » Fri Jun 20, 2003 6:55 pm

you talkin to me or subyluvr?

ciper · Post by **ciper** » Fri Jun 20, 2003 10:03 pm

subyluvr2212, because he changed the close position of the IAC

subiekid · Post by **subiekid** » Sat Jun 28, 2003 4:29 am

i have the same issue as subyluvr2212, my motor shakes really bad when it goes down to like 700 rpm, but then goes back to 800 and is ok. when i have the a/c on is the only time that my car will idle good. the guy that did my motor swap told me that he changed the idle screw to see if it would make the car run better, he said the ecu just compensated for every turn of the screw. i also think i am running most of the valves and sensors from my ej22. i have the manifold from the ej22 on my ej22T block. all of these things are on the intake manifold so that could be one of the reasons for my bad idle. once i get my obdI ecu in i will know if it was all just the ecu.

sullione · Post by **sullione** » Sat Dec 27, 2003 6:20 am

Sorry guys, but I need to ask this for a little help after reading this post. I think I may have IAC issues. When I start my car, sometime it idles high...then low...then high again before settling at the normal spot. It did this when I first got it and took it into the Subaru specialists in Alaska and they swapped out the temp. sensor which fixed the problem. Well the systems have returned but every now and then I get this high pitched whistle sound from somewhere in the engine bay. How do I tell if the IAC is the problem or something else like the temp. sensor. I must say that I think it'll be the IAC more than the temp sensor by process of elimination (temp sensor was changed at 52 something thousand miles.

Post by **Legacy777** » Sat Dec 27, 2003 7:39 am

Look at the gasket on the IAC valve.....is it thick (sandwich type gasket), or very thin piece of metal.

If you take the electro magnetic top off the valve (mark the position if you take it off) does the valve turn freely? If it doesn't that may tell you your answer for sure.

123c · Post by **123c** » Thu Jan 01, 2004 3:07 am

Would the IAC valve cause the CEL to come on?

ciper · Post by **ciper** » Fri Jan 02, 2004 12:17 am

If the curcuit was shorted or open it could. More likely a failed valve would cause stalling, high idle or bouncing idle.

123c · Post by **123c** » Fri Jan 02, 2004 2:16 am

ciper wrote:If the curcuit was shorted or open it could. More likely a failed valve would cause stalling, high idle or bouncing idle.

I might have a failed one, because sometimes the idle will drop down to 500rpm when I am at a stop light, and sometimes it seems to be idling too high. If it is bad, would it also cause bad gas mileage?

Post by **Legacy777** » Fri Jan 02, 2004 3:33 am

Anything's possible. if you suspect the IAC, test the valve and if doesn't pass the tests, get another one.

ciper · Post by **ciper** » Fri Jan 02, 2004 3:39 am

I say try to get one from the junk yard in decent shape and clean it up real nice. Then swap it for your current one (retain your electronic portion) and see what happens. I did this on my buds legacy. His idle would go from 1200-500 2 times a second and slowly smooth out when the car was started.

The same car is currently 3 feet in the air in his garage, it will be the first transmission swap I have done all by myself so it should be fun!

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Interesting IAC tid-bit

Interesting IAC tid-bit