Den Leisten

What does this valve do? How does one know if its good or bad? Can't find test procedures. What is the static position of the valve,open or closed? Does anyone know how it interfaces with the vacuum limiter and the auxiliary air regulator?

Peter Zimmermann

The valve is open cold (to create a satisfactory cold idle), and closes as the valve warms up (via 12V). It's a part that is super-reliable; what difficulty are you trying to diagnose?

Den Leisten

I believe you are referring to auxiliary air regulator. I need info on the aux. air valve sometimes called aux air supply or additional air valve. 911 110 273 01 it has no electrical connections. No specific symptoms. I just pulled the engine for a vacuum leak and was checking all the other components before reinstalling. Can't find any specs on this valve.

Peter Zimmermann

Ah yes, it would have been so much easier if Porsche had just numbered these parts! The aux. air valve (AAV) is somewhat mysterious, so much so that most have the vacuum hose disconnected and plugged! For trouble shooting purposes (I'm not even sure that Porsche knew what they did) the problem caused by either the AAR or AAV are idle speed related. The problem can be high idle at temperature, or no speed increase cold. If you have neither symptom the AAV "should be" OK - I've never replaced one because of any other reason.

Den Leisten

Thank you Pete
Den

brad-cam

I thought the flat "pancake" valve with the vacuum hose is the "deceleration valve" and the other one that looks exactly like it but without the vacuum port is the AAV (?) I had a stuck high idle when my decel valve failed. Disconnected and plugged the vacuum hose and it ran great, albeit engine speed drops quickly to idle when you lift throttle and depress the clutch so rev matching gear changes takes a little more care, or just shift quickly (if your 915 lets you ). Makes it more fun to drive though with fewer control systems getting in the way.

Peter Zimmermann

Hah, my bad! I reverted back to language that we used at the shop, and didn't consider the confusion factor. We used to call the AAD (Auxiliary Air Device, aka Vacuum Control, aka Decel Valve) on earlier cars the decel valve, and to avoid confusion we called, on '80-83 cars, the lower AAV (near cyl #6) the lower valve, and the real AAV the upper valve (which was in the lower position on '76-79 cars). We actually were able to correct some idle speed conditions by plugging the small vacuum hose to the lower valve - that's where my comment came from about even Porsche not knowing what the valves did (we swore that they put them there just to snooker the EPA!)! We were never able to "fix" a symptom by doing what the factory manual said, but we kept one each of the valves in stock for those "what the hell, let's try it moments." Sorry for any confusion!

Den Leisten

I'm beginning to understand. The upper AAV valve with no additional vacuum line is still in question. I can blow air through this valve when I hold it in my hand. Valve is open. Is it always open? Is there a baffel inside that closes? Should I just remove it and plug the lines?If it's always open what good is it? My decel valve is ok.(AAD)

Peter Zimmermann

I don't think that blowing into it is a good test, the device is operated with vacuum, so does yours close when you apply vacuum to one side, the hose connection that's off-set, not the one in the middle?

Den Leisten

No it doesn't close with a suction applied to the outer connection.

Hobbsie

The one with vacuum line should be normally closed, then open with vacuum applied.

The one with electric plug should be open when cold; the electric heating element closes it as the engine warms up.

GothingNC

Pete,

Over the last couple of weeks I noticed that my idle after a cold overnight start would jump up to about 1,100 RPM for about 10 seconds and then drop down to about 700-800 RPM while the engine is warming up.

About 15 minutes later it goes back up to to around 950 like a switch was turned on.

It is an 82 with 9.7 Compression, SSI's with the intake ports and runnners blended to 36MM and Elgin SC330 Cams. New injectors, sleeves, O-rings, gaskets etc.

The 02 sensor is disconnected in the negine compartment and the CO was set to 3.5% just before I picked up the car about 8,000 miles ago.


So after some research I found this thread and was wondering if my symptoms are related to a failed AA valve?


Thanks


John

Houpty GT

Your AA regulator is working correctly from all the test that I have done. What happens is that there is an electrical heater in the valve and it does not take long at all for the valve to close. You could disconnect the electrical connector to greatly prolong the high idle if you wish. I have also seen a post on Pelican where someone re-wrapped their heater inorder to get a longer high idle. I was thinking of just adding a resistor in line to reduce the heater voltage.

GothingNC

Houpty,

I'll just leave it as is.

Thanks

John