AAR Check/Adjust update 12-10
Posted: 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
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