AAR Check/Adjust update 12-10

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AAR Check/Adjust update 12-10

Postby Amskeptic » Mon Feb 15, 2010 5:15 pm

AAR - Auxiliary Air Regulator

So lots of us seem to have cold/hot idle issues associated with our axiliary air regulators. I scored one at the Pick-n-Pull recently to trouble shoot the one currently on the bus. Since I had to test it prior to install, I figured I'd document for the community.

The AAR functions like a carburetor's choke fast idle cam. It provides extra air to the cold engine to overcome heavy cold oil drag and to provide additional air for the rich cold fuel mixture ordered up by the ECU. When it's not functioning correctly, you experience either a low cold idle (the AAR aperture not opening enough) or a fast idle when the engine is warmed up (aperture not closing).

The AAR is located in front of the oil breather and behind the right rear intake runner (cyl #2) shown below. The little rubber elbow on the right is an often overlooked vacuum leak source.
[albumimg]2750[/albumimg]

Here's a side view of a cleaned up AAR (note the yellow crap on the little bolt--that's the factory adjustment sign-off where you will adjust if necessary):
[albumimg]2753[/albumimg]

Here's a photo showing the aperture open in the middle of the AAR. Note part number. The aperture was open at ambient temps this morning of around 55*. Perfect.
[albumimg]2751[/albumimg]

Here's a (bad) photo showing the aperture closed after sitting in a hot (250*) BBQ (flame off) for 10 minutes. There is the smallest needle hole still there but it's acceptable in my book.
[albumimg]2752[/albumimg]

The third test is for resistance. You want around 30 ohms. Hook up your meter thusly:
[albumimg]2748[/albumimg]
Read said meter:
[albumimg]2749[/albumimg]

Ritter

ADJUSTMENT

If engine is suffering a fast idle when warm, try first merely cleaning the mechanical end with GumOut carb spray followed by a nice bath of WD-40. Keep the electrical plug up vertical through this cleaning procedure.

If engine is suffering a doggy slow idle when cold, remove the AAR. Stick it in the freezer for ten minutes or so to get enough of the aperture window open that you can cram a 2 or 3 mm allen wrench through the window. If freezer persuasion is insufficient, try to pry the disk with an awl or small-bladed regular screwdriver. Once you have the allen wrench through the opening, loosen the adjustment screw's locknut. This adjustment is *not* about rotating the screw and watching the aperture open. It actually sort of slides around, so jam that allen wrench to get the aperture as open as you can, and harass the adjustment screw to find it's relaxed state with the aperture open, then tighten the lock nut down. There are intense leverage/fulcrum points going on between the bimetal and the disk, so if you get it right, it really does remain more open. There may be a little closure when the allen wrench is withdrawn, but if it springs back towards closed dramatically, repeat adjustment attempt.

Await the cold morning with great anticipation. You can hear that little sucker suck from the driver's seat as the engine fires up and holds a strong idle on the coldest morning. Then, in about 4-6 minutes, the idle will trend towards the normal warm idle.
Colin 12-13-10
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Re: AAR Check/Adjust update 12-10

Postby Randy in Maine » Fri Apr 01, 2011 7:45 am

Did the pictures go away for this?
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Re: AAR Check/Adjust update 12-10

Postby Amskeptic » Fri Apr 01, 2011 7:49 am

Randy in Maine wrote:Did the pictures go away for this?


Must have been when we had to upgrade the site under duress.

I will ask Ritter.
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Re: AAR Check/Adjust update 12-10

Postby Ritter » Tue Apr 12, 2011 6:44 pm

A little late to the party. I didn't remove pics from the original post. Crap, it looks like my photos got whacked from the IAC. Colin, I need you to talk to cousin Vinnie about that....  :blackeye:

If there are requests, I'll try to recreate the original thread. Lemme know.
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Re: AAR Check/Adjust update 12-10

Postby chitwnvw » Tue Apr 12, 2011 8:00 pm

Doggone IAC!!!  I have an  aar pulled and am cleaning, if you want some oven and post oven shots.
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Re: AAR Check/Adjust update 12-10

Postby dtrumbo » Tue Apr 12, 2011 8:02 pm

What method are you using to clean it?  I don't think soaking it in solvent would be good because of the plastic connector and such.  Perhaps soda blasting?  I have one out that I need to clean up so I'm all ears.
- Dick

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Re: AAR Check/Adjust update 12-10

Postby chitwnvw » Tue Apr 12, 2011 9:18 pm

Oven cleaner.
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Re: AAR Check/Adjust update 12-10

Postby dtrumbo » Wed Apr 13, 2011 5:19 am

Spray it on, let it soak, rinse it off?  Or do you spray it on and actually put it in the oven?  If so, how long, how hot?

So many questions...
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1979 Super Beetle convertible.

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Re: AAR Check/Adjust update 12-10

Postby chitwnvw » Wed Apr 13, 2011 9:24 am

dtrumbo wrote:Spray it on, let it soak, rinse it off?  Or do you spray it on and actually put it in the oven?  If so, how long, how hot?

So many questions...


I haven't actually put it in the oven although a low heat would probably help, at least that is what the directions say.

What I do is spray it with some industrial strength degreaser rinse and then coat liberally with oven cleaner.  The oven cleaner seems to work best when it is allowed to soak, even to the point of drying out, then I rinse and repeat.   Those steel wool oxy soap dish cleaners work really well too, that is usually what I use for the final rinse.  Then allow to thoroughly dry.
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Re: AAR Check/Adjust update 12-10

Postby airkooledchris » Wed Apr 13, 2011 3:56 pm

Click images to view full size

3 - 250* and it's fully closed
4 - 3 minutes of cooling
5 - 6 minutes of cooling
6 - 20 minutes of cooling
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Re: AAR Check/Adjust update 12-10

Postby Amskeptic » Fri Apr 15, 2011 12:45 pm

GumOut is an excellent cleaner, just keep the plastic connector pointing up. Use finger to block lower opening while you spray in other opening. Shake well. Drain. Repeat. Allow to air dry.
Colin
BobD - 1978 Bus . . . . . . . . 105,077 miles
Chloe - 1970 bus . . . . . . . . 153,230 miles
Pluck - 1973 Squareback . . 55,480 miles

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Re: AAR Check/Adjust update 12-10

Postby airkooledchris » Mon Apr 18, 2011 1:41 pm

I pulled my AAR and indeed it appears to have been sticking, in that it wouldn't full open.

This is how far open it would be when dead cold:
109

This is after cleaning it up. I did confirm that after 10 minutes at 250* it did still fully close....

110

Going to install it after work and see how it effects the cold and warm idle characteristics.

I have a spare that seems to work great, but this one showed 29 ohms and the spare was only 27* so I figured id clean up the original and try it out first.

thanks as always for the resources here. I wouldn't have ever guessed you could just re-adjust it after cleaning by loosing that screw on the back.
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Re: AAR Check/Adjust update 12-10

Postby Gypsie » Tue Apr 19, 2011 9:31 am

Would pic #2 be considered "full open"?
So it all started when I wanted to get better gas mileage....
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Re: AAR Check/Adjust update 12-10

Postby airkooledchris » Tue Apr 19, 2011 11:06 am

Gypsie wrote:Would pic #2 be considered "full open"?




It seemed to match up with my other working unit in it's 'full open' state, so for now - im assuming so.

UPDATE: dead cold this morning I fired it up and it idle'd nicely around 900+ RPM, and once fully warmed up it idled just a touch higher around 975RPM's

checked timing and was at 3* ATDC, and 28* max advance with vacuum pulled and plugged.

my head temps have been high under load lately so I do currently have the O2 sensor disconnected, with the idle adjustment screw out about 4 turns. this is with a NOS AFM installed for my california specific model, which otherwise seems to want the whole thing running on the lean side.
I only mention the part about the sensor and lean/rich running as while I know the AAR had a big effect on the warm/cold idle, im sure this plays into the results to a degree as well. (though I had the same cold/hot idle issue with the O2 sensor connected, FYI)
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Re: AAR Check/Adjust update 12-10

Postby fancy pants » Wed Jul 13, 2011 1:02 pm

Is there any chance to get the pics from Colin's original message to appear??
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