odonnell

Also called the 'auxiliary air valve' and 'cold start valve', it's the one responsible for allowing a little air past the throttle blade when the engine is cold to help with cold starts. I'm pretty sure mine is bad, the car idles low when cold but is great when warm. Sometimes the car dies immediately after starting, which is slowly annoying me into replacing it.

Porsche Part# 944-606-103-01M 100
Bosch# 0280140169
Standard# SMP-AC351
BWD# 22660

I've heard you can get the part from BMW, Saab, VW, and even Citroen (?) but am curious if anyone has actually done that. I'm looking for a new unit, anyone have a vendor they recommend that has the right part for cheap? (<$60). Of course the OE part is NLA, at least on Pelican.

Edit: so far this is the only thing I could find, and it looks pretty used.

V2Rocket

Check that your throttle blade isn't cracked open more than it should be. Does it idle a little high when warm?

Chances are...you could use pretty much any such valve from any car with a compatible electrical connector. It only does one thing.

944Ross

Lart has a bunch for sale, last time I looked.

odonnell

I intentionally had the throttle blade slightly opened at one time to bypass the stupid fuel cutoff whenever I clutched in (by making it so the TPS idle position never activates) but I've set it back now that I have a late DME in my car. I'll double check, but I'm pretty sure it's either the AAR or the ref sensors causing this. I have the idle set a little high (via the large screw on the left side of the throttle body) to compensate for the low cold idle. Hence, it idles at 1200 warm now. No vac leaks. Wonder if the increased throttle speed is letting enough air past the blade to make starts sketchy.

I'll talk to Lart, thanks for the tip.

Dougs951S

Michael, I doubt that having the idle speed screw opened up a bit to raise the idle would effect your cold starting. We have discussed this before, my 83 was setup the same way, it idled at 1100 warm and the idle contact on the TPS never engaged. Car ran great hot or cold. Next time we get together we can play with it, you probably don't need the AAR now that you've got a late DME, remember the late cars didnt have the cold start valve, only the Idle control valve. I'd recommend deleting all the lines to the AAR and trying to get the car to idle well by adjusting the throttle stop so that the idle contact does engage, and letting the idle control valve take care of the extra air flow needs on cold starts. Remember the ICV wont engage if the idle contact on the TPS does not properly function.

V2Rocket

Doug, the early cars only had one aux air valve for cold starts, there was no icv until the late cars came along. It may be the DME is trying to control the AUX air valve as if it were an ICV though.

Early cars also have a secondary air valve but it only operates when the a/c is turned on

Dougs951S

Spencer thanks for reminding me! Its been some years since I've owned an early car so I'm admittedly a little fuzzy. I think what is more likely is simply that the early car's cold start valve is not being controlled at all by the late DME, leaving it stuck shut and starving the motor for air when its cold.

odonnell

My impression was that the AAR gets power when the engine is running and after a minute or two, the internal mechanism closes and no more air bypasses the tb. Guess I should get the multimeter out and make sure it's getting 12v to begin with.

Tiger03447

Try putting vacuum to the inlet with a hand pump and see if it opens or closes totally...If this is the valve I'm thinking of, mine has an adjustment on the top and two vac lines running in and out of it...for my '83. maybe I need to check it out more thoroughly though...didn't see an electrical connector..wrong part?

V2Rocket

i know this is a dead thread but i figured id put answers down for future searches, as i was doing looking for AAR info.


the aux air valve turns on when the car is started cold. eventually the metal contact spring inside gets heated which causes it to close the valve (by then the car is warm enough to idle well)

youre looking at an emissions device - the idle valve/aux air valve is under the intake manifold between #2/3 runners

odonnell

Thanks for the info.

I nabbed one from the junkyard to mess around with it. I cleaned it out with carb cleaner. After I made these videos, I ran seafoam through it, and a lot of little black crumbs came out. So that seems to be a good solvent to use, I'll re-run this test later on to see if the results are different.

Tiger03447

Dear Mike: Great videos! now I know how these work and what I have to do to check mine! Thanks a bunch!
Tiger 03447

odonnell

No problem!

I did a second test today using a legit laboratory power supply.

Initial current draw: 0.388 A

Steady state (final) current draw: 0.384

The "notch" (bottom indent in the opening) was enclosed at 0:55 and the valve closed completely at 2:05.

This differed from the video where I used a Dremel charging station which was rated at 500 mA. The AAR pulled 388 mA (max) so I'm thinking the change was due to running seafoam through it. After all, a lot of black crumbs came out, which I'm sure could have obstructed the valve in some way. This time, it closed completely and didn't taper off at the end like it did in the video. Nice linear response.

On the other hand, I'm not confident that ~2 mins is enough time to allow my motor to get to a nice idle (I need about 970 RPM due to balance shaft delete and custom milled crank). I'll mess with the nut and see if I can prolong the valve closure to ~4 mins (double).

Edit:

Ran a few more trials and got consistent numbers.

Also decided to mess with the small nut on the back, and can confirm that it allows you to change the valve characteristics. Removing the nut reveals the stud protrudes from an elliptical hole:




If you loosen it slightly and push it toward the outside edge of the part, the valve opening gets larger and take longer to close off. On mine, it took 2:10 to enclose the bottom notch and 4:30 to fully close (both about double the stock position which was in the middle). So the idle would be higher at first, and the valve would affect the idle longer.

I haven't tested it with the nut all the way on the inside edge of the hole but the valve opening was smaller as you would expect.

odonnell

Quick question. Is this thing supposed to create a complete barrier when it closes?

I have it sitting in front of me, has been getting 12v for about 10 mins and the valve is fully closed. I can tell it's in steady state because the current draw tapered off.

When I blow through it, it has some resistance, but largely does little to impede the air flow. Is that normal? Is it only designed to somewhat hamper the bypass, or is my unit busted internally?

V2Rocket

do you have a way of checking if the input voltage shuts off at a certain point, or is the AAV always getting power but just closes due to its design?

i would think that the "additional AC air valve", mounted to the back of the airbox in AC-equipped cars, would suffice if it's just an on/off design. that valve allows more air into the manifold past the throttle so the car idles better while under load from AC system...works well enough with its little hoses. even draws air from/deposits air to the same places as the AAV....and they are everywhere (never heard of one failing so they should be cheap!)