IAC Valve adjustments

[L.Michael]

Can you adjust the IAC with the setting screws on top? I read both ways on this, more so on that one shouldnt touch them, as they are set by factory.

I've tried pretty much everything else, from setting the TPS, seafoaming the intake & IAC Valve directly. New plugs, throttle cable... Still, my idle speed goes all the way down to say 600rpm. I reset the computer by disconnecting the battery, figuring that after I cleaned everything, this would need to be done as well. However, as I've said, still a lower than expected idle speed.

I've read that the idle RPM should be at about 800. Sometimes it gets even lower than this:

https://sl-i.net/FORUM/images/imported/2013/05/369a00de839a43e3a6c9954a807dbecc_zpsfa1d-1.jpg

[Odycee]

You can't base on your eye with analog instrument to guess RPM is 600. It looks normal and as long as it's not choking, it looks fine to me. Mine idle at 700 actual ECU read from obd2 Torque app. I think you're just paranoid. Does it idle smoothly?

[Wiscon_Mark]

That looks pretty normal to me for a warm day and a warmed up engine. My Outback would sometimes dive a little when the A/C compressor kicks on, but it never killed. I probably had it like that for 6 years. I don't think you need to worry.

[zoomzabba]

My idle on a cold day will finally settle around 720. Hot days see 680. This all confirmed with the Torq app.

[anothernord]

Standard idle speed is ~700 RPM.

Have you actually removed the IACV valve entirely and really scrubbed it out? Test the resistance between pins 1-2 and 2-3, you should read ~9 ohms.

[L.Michael]

The Torq app? whats that about?! I'm assuming it's an iphone app?

It's less the visual of where the tach is, but rather that when I drove during winter, and having the alternator run the rear defog and seat warmers, is where my greatest concern is, as it didn't seem to be rev'ing high enough to run the electrical system efficiently.. and since it does, visually, show that its idle is around 650 or so, is why i figured there was an idle problem.

Since you're saying idle is 700, and not the 800 I otherwise read, then it's not so far off. I hadn't taken it off at all, as of yet, but I did use seafoam and ran that through the IAC.

[Odycee]

700 RPM for manual, looks like you got 4EAT should run 800 RPM idle when warm. During winter time when cold start it should run 1200 RPM then reduce to 800 RPM. It appears you need to clean your TB and IAC will fix this issue. When was the last time you change plugs?

Torque app ($5) will work for Android or Apple smart phone however if you use ELM OBD2 bluetooth device it works only on Android phone or tablet such as Samsung, HTC, Motorola. If you have an Iphone, you should buy Wifi OBD2 device such as PLX Kiwi. Apple has a proprietary bluethooth protocol, you have to pay some $60 to get that SW to run on ELM device. With this app, Torque SW gets info directly to car's ECM then translate to human interface so you can read them in both digital or analog format. It reads your CEL codes and clears them too.

[L.Michael]

I did a lot of work over the last half year on her, including new platinum plugs. Unless there's more to it, I did a lot of seafoaming to the intake, as well as in the oil itself when I changed over to synthetic recently. The system otherwise seems to run smooth, just the morning piston slap when I first start it, and then when its warm, and at idle, it likes to drop low and sometimes give a small shudder.

[Odycee]

Change the air filter? clean the MAF?

[L.Michael]

air filter is a fram crap, but its clean. the MAF was just cleaned as well. Just used the spray, no dic'n around with a Q-tip.

I'm still wondering if IAC valve is in fact adjustable. It sure looks like it is.. or is that how the resistance is set?

[Odycee]

IACV is computer controlled, don't mess with it. Did you actually remove IACV to spray it or spray into TB only? I removed mine and a lot carbon build up around the valve. The resistor is a fix value, it gets the info (hot/cold) from the ECM to send out certain voltage to control open/closed the IACV. Don't ever touch the MAF thermistor, that is a temperature variable resistor, just spray to it only. If you MAF died, you would get a ton of fuel in your injectors, flood the damn thing, fuel smell, and car will never turn over.

[L.Michael]

I've tried pretty much everything else, from setting the TPS, seafoaming the intake & IAC Valve directly.

http://www.seafoamsales.com/sea-foam-spray/
I used this to do both the intake, as the tutorial shows. As well, similarly, I took off the intake connection after the MAF, shoved the tube down the IAC supply, replaced the intake back onto the MAF, and sprayed it while the car ran. Just like every other time after I shut it off and then ran it again, it blew a bunch of white for a while. I'd say it runs a bit more smoothly now, but no change to the idle speed...

Perhaps it is the computer.. Or a resistor somewhere?!

[Odycee]

I lied....but it won't be easy. This is off an 99-01 Impreza doc, make sure you have the same TPS.

You can adjust your idle with TPS by slide up/down the unit so do NOT unscrew completely. Rotate until you idle correctly. Or, you can read pins #15 and #17 from the ECU with an DVOM and adjust until the DVOM reads .45-.55v


https://sl-i.net/FORUM/images/imported/2013/05/TPS1_zps4cff3056-1.jpg

[L.Michael]

I've tried this last summer already, and it adjusts it, until the computer learns it. Then it idles back down accordingly. Same thing when you adjust the throttle cables a bit. The computer circumvents the settings.

[Wiscon_Mark]

I wouldn't recommend messing with the TPS just to screw with your idle. It's not there as an idle adjuster. TPS should only be adjusted so it's reading the throttle correctly which means you either need an Ohm meter hooked up to the harness or a scan tool that tells you throttle position.