IAC adjustment

snowjob · Post by **snowjob** » Mon Jul 25, 2005 1:07 pm

So when my EJ20 came in, my bros was undoing everything to see what it was and then putting it back together. Well the brainiac undid the IAC(idle air controller) and did not put it back in the factory spec location. Does anyone know how to properly adjust this sucker?? My idle is really crappy at the moment and I know that is what is causing it.

vrg3 · Post by **vrg3** » Mon Jul 25, 2005 3:18 pm

I take it the little white paint markings that show the factory location are gone?

There is no defined procedure for recalibrating it -- the official procedure is to remove the valve, place it in the trash, and install a new one. Sigh.

All I can suggest is to keep adjusting it a little at a time. After each adjustment, reset the ECU, so it doesn't remember any of the hoops it tried jumping through last time when trying to make the engine idle right. Of course, have the engine warmed up the whole time.

snowjob · Post by **snowjob** » Mon Jul 25, 2005 7:17 pm

So I need the engine to be warmed up to get this sucker reset? so If I adjust it till it idles at 750rpm at idle and then shut it off and disconect the battery, for 10 to 20 min, reconnect it. It should be OK?
Let me know if this is what you meant.
Thanks
frazer

vrg3 · Post by **vrg3** » Mon Jul 25, 2005 10:41 pm

Well, having the engine warmed up means you won't have that variable (coolant temperature) in your testing. If the engine isn't warm, then it will start to warm up while you monkey around, and it'll affect both what the ECU's doing with the electromechanical portion of the valve and what the bimetallic portion of the valve's doing on its own.

That's not exactly what I meant. The problem here is that the ECU tries very hard to learn to idle. In the presence of an idling anomaly, it continuously changes how it drives the IAC valve. So, what you need to do is reset things after every adjustment you make.

So -- something like this:

1/ Start engine with A/C turned off.
2/ Let engine run until radiator fans turn on. This means it's warmed up fully.
3/ Shut engine off.
4/ Reset ECU by disconnecting negative battery cable and holding brake pedal for 30 seconds, and then reconnecting the cable (reconnect it fully; not loosely).
5/ Start engine.
6/ Note whether idle speed seems high or low after giving the engine maybe 5-10 seconds to stabilize after starting.
7/ Stop engine.
8/ Adjust valve (only a tiny bit!) according to results of step 6.
9/ Repeat steps 4 through 8 until satisfied.

THAWA · Post by **THAWA** » Tue Jul 26, 2005 3:05 am

Of course you want to make sure that the engine stays at operating temp while you're doing this.

vrg3 · Post by **vrg3** » Tue Jul 26, 2005 3:14 am

Good point... maybe it'd be good to wait a little while between steps 6 and 7 every once in a while.

NICO · Post by **NICO** » Tue Jul 26, 2005 9:59 am

when i change mine it messes with the idle + plus the boost, if my car runs below the half mark on the temp sensor its ok right.

would more gas give a low temp or messing with that iac, all i no is i can rev and boost the shit out of it, and the motor will not even go near the half mark.

its a good thing and i get killer i mean killer gas milege now.

snowjob · Post by **snowjob** » Tue Jul 26, 2005 2:07 pm

I just sprung a leak in one of my injectors, fuel is pouring out the top of injector number 1

which sucks because I have to drain the coolant resevoir to get to it. Related???maybe caused by an engine that has sat for over 10 years HMMM maybe.

vrg3 · Post by **vrg3** » Tue Jul 26, 2005 2:21 pm

Nico - It's supposed to be pretty close to the halfway mark... you might want to hook up my scantool or install a gauge to see what temperature it's actually running it. The air/fuel mixture and IAC valve shouldn't have much if anything to do with operating temperature.

Snowjob - D'oh. I guess it'd be a good time to replace all the O-rings...

NICO · Post by **NICO** » Tue Jul 26, 2005 6:17 pm

i will check and let you no what it says i can use the subaru scan tool to do it right, the one you made does not want to work on my car.

vrg3 · Post by **vrg3** » Tue Jul 26, 2005 6:18 pm

Yes, you can use the Subaru scan tool. That's weird that the Subaru tool would work and mine wouldn't, though; they're functionally identical if the laptop is working right.

snowjob · Post by **snowjob** » Tue Jul 26, 2005 6:54 pm

has anyone else ever had their o rings leak out of the top?

def09 · Post by **def09** » Tue Jul 26, 2005 8:24 pm

Do you mean the throttle position sensor?

vrg3 · Post by **vrg3** » Tue Jul 26, 2005 8:26 pm

We're talking about the idle air control valve (just below the PCV valve). By loosening the two screws on the top, it's possible to adjust the static position of the valve.

def09 · Post by **def09** » Wed Jul 27, 2005 2:37 am

[quote="vrg3"]There is no defined procedure for recalibrating it -- the official procedure is to remove the valve, place it in the trash, and install a new one. Sigh.
I hadnt noticed the iacv had white markings on it. I think for that you summed it up perfect. One of those items you should not tinker with the insides.

vrg3 · Post by **vrg3** » Wed Jul 27, 2005 2:43 am

def09 - Yeah... Don't touch that screw!

snowjob - Have you tried seeing if you can swap a known-good IAC valve from a North American Legacy (turbo or non-turbo) onto your EJ20 intake manifold? The plumbing might be slightly different but it might not be that big a deal.

snowjob · Post by **snowjob** » Wed Jul 27, 2005 10:32 pm

Unfortunely the part numbers are different between the two. I'm going to try your manual tonight and see what happens.

vrg3 · Post by **vrg3** » Wed Jul 27, 2005 10:39 pm

I realize the part numbers are different. It still might work. The internals of the valve are probably very similar, if not the same. For example, the part numbers are different between a 93 turbo and a 93 non-turbo, but the only difference is that the turbo valve's inlet pipe curves upwards while the NA one just sticks right out.

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IAC adjustment

IAC adjustment