rockatansky

Today I will go to customs to get the light gun to check the timing in the car (after 3 years stoped by PO). While I wait these past days I have removed the aux air valve and tested to see what it does. Here are the results. Love to hear your opinions about it:

Heat test applying volts:

Cold test putting into the freezer for more than an hour:

Some more information:


My original thread with the full process awaking the car here:
https://rennlist.com/forums/928-foru...ml#post8852075

Bart-Jan

Great! That are some interesting images; I was wondering wether mine functions and was thinking of doing something similar. Since it's for cold starting only, to increase the revs, all you need to know is wether it closes properly after heating up. Yours does, so to me that seems fine.
There's one thing I would check if I were you: check the lines, fuse etc. for the voltage on your plug; it seems very low to me.

Lizard928

Bart-Jan,
You run MS you should switch to a two wire PWM valve off a VW golf for more control.

NoVector

Great video—love the theme music! I think I now understand the purpose of the pump: the valve is open when it’s cold to pump air into the exhaust and dilute the bad stuff. Then, as the engine/cats heat up, no fresh air is pumped into the exhaust. So it's only purpose is to meet an EPA standard while the engine/exhaust is cold(??)

rockatansky

Thanks. Because I'm completely new about mechanics my only way to collaborate is to post videos and stuff like this. I have read many threads about the AAV with explanations of how it works so I decide to record on video to share for the people who is wondering how it goes. (about the music I couldn't resist )

I didn't mention in the post, but my doubts, after reading here and there, are:

- Has my valve enough opening when out of the freezer. I suppose it should be completely open.

- Is it normal to have 10.63V at the cable while the battery has 12.36?. I recently remove and clean and put some stabilant in the contacts of the electric panel following the sharkskin tutorial. If it is not normal what should I check?.

- Is it normal to have 21 ohms of resistance at the valve conector?. If I'm not mistaken at the WSM says it should have between 45 and 70 ohms.

Bar-jan,
You mention the voltage is low in your opinion. Ok, thanks, let's see what other people say and how I could find the reason.

NoVector,
sure somebody with a deeper knowledge than me will explain you the purpose of the valve closing when hot.

jon928se

Bruce

Agree on the music.

Your 93GTS does not have this AAV - does not have anything to do with the airpump.......

Rockatansky has an '80 with CIS mechanical fuel injection - needs the AAV to raise the idle speed when cold to keep the engine running.

jpitman2

MY car had a pretty low idle when stone cold in winter (~50-55F), and at one stage began to stall after I had driven a few 100m and paused in gear. When I looked in the AAV, it was probably half open , similar to above. Since I had a good steady hot idle (and slightly higher with AC on), I reckoned AAV was the cause of the cold idle issue. I drilled out the 4 rivets, put it in the freezer for a while to get it as open as possible. I then bent the post holding the end of the spring thats trying to close the valve, until was maybe 80% open, and then checked that it got close (95% at least) to closed when warmed up. Sealed it back up with some short bolts (M6, maybe M5) and nylocs, and refitted. After that, cold morning, she spent a minute at ~1000rpm (and no stalling) before slowly coming back down to the usual 750 +/- 50rpm. To me it would be acceptable if it didnt quite fully close hot, and you had to adjust the idle screw a little, as long as it was stable in its most closed point, and didnt move around.
If you dont have an idle problem during warm-up, I wouldnt mess with it, but if there is a problem, try the above.
IIRC this same AAV was used on the L-jet units, but its not on the LH systems, as they have an idle stabilizer valve.
jp 83 Euro S AT 53k

rockatansky

Thanks!, I have a clear picture now of the behavior of the valve. I open it to check if it moves or not and seems it closes nicely. The problem could be when opening at cold... not enough I think. I will try first to spread some WD40 or similiar and make more tests with the freezer to see if it opens more.

The behavior of the car is: With the AAV in place, very low revs (400 with stalls here and there) when cold, very delayed response when pressing the throttle, and stalls when doing test drives even being hot (aav already 100% closed having my video in mind).

If I remove the front hose from the AAV, the car won't start (at 78F exterior temp this days).

I need to check the timing first, as WallyP advice me (I already got the light), and start from there to see if I raise the revs which are low all the time and get a better response from the throttle, I will do that before touching throttle screw or fine tunning the AAValve.

...but I would like to ask a funny one here. I have two hoses coming out from the T's before and after the Aux Air Valve and going to nowhere... better said going to a fuel filter! and then nowhere. With the attached picture I show it better.

Don't worry, no fuel through this hoses. Previous owner must have done some creative plumbing and put the filters there, don't know with what purpose. Does anybody has a clue?.

I already comment on this in my thread 'awaking after the 3 years', but it was on an early stage where I still haven't started the car and didn't pay too much attention to those two hoses when I saw they were not related with fuel. I think now is the time to check those hoses, know where they should be connected, and get rid of them, cap them, or whatever to avoid affecting the normal behavior of the car.

jpitman2

It should not run if you pull the front hose off the AAV - huge air leak, no fuel will get delivered.
I cant quite visualize what my small hoses do where you have the filter things, BUT there should be a small solenoid with a hose in and a hose out, and 2 wires connected, clipped to the cross brace - this solenoid is fired when the Aircon is running, and it allows some extra air in to lift the idle to handle the Aircon load. These dead hoses look like they should be connected to this solenoid, which i dont see.
I am sure there is a picture here somewhere of what you should have.
jp 83 Euro S AT 53k

MartyCee

Hello Listers,

Even though its a few years later, I'd like to clear up what the aux air valve actually does and how it affects your running engine.

There seems to be a few posts here that create a bit of confusion. There was a mention that its to pump air into the exhaust for EPA reasons whilst cold, which is not the case.

On a cold start, the valve is open to allow more air to bypass the throttle into the air intake plenum to increase idle speed, whilst at the same time the cold start injector will be spraying fuel into that airstream, thus creating a richer mixture for startup. As the AAV closes (due to electric heater + engine warmth) the extra air flow diminishes. During that time the cold start injector (CSI) will have cut out because the warm up timer sender (on the base of the Warm Up Regulator) would have cut off the power to the cold start injector. When all this has happened the idle speed should be now at normal operating range, and the car warmed up sufficiently not to need a richer mixture.

Please note that this airflow is air that has already been metered, which is why it runs poor if leaky or removed hose(s), as any leaks will introduce unmetered air, and will cause poor performance.

So to check it's working properly, you need to ensure that the AAV opens and closes as mentioned in the previous posts AND you also need to ensure that the Cold Start Injector is getting a voltage to operate until the AAV closes where the Cold Start Injector should stop well before, AND you need to ensure no air leaks (the hoses expand and become extremely hard when old to the point you can turn them on the T pieces which is a sure sign there is an air leak).

To fix rockatanskys issue, Check the AAV works as per the posts, check the CSI (Cold Start Injector) is getting a voltage when cold, and that voltage disappears before the AAV valve is fully closed.

The two hoses with fuel filters on them :-) are supposed to be connected to the air conditioner auxiliary air valve, which appears to be missing on your car (it should be attached to the crossbrace). If you cant put it back, then plug both those two hoses off (closer to the T pieces) and you should be right.

Chopperharris

Old post but the above is not quite correct. The cold start injector only fires for about 4 to 10 secs during starter cranking. It’s doesn’t keep firing until the AAV closes - if it does it’s leaking. It‘s the WUR that works in conjunction with the AAV when the engine is cold - allowing more fuel to flow to compliment the extra air from the AAV. The CSI is the equivalent of spraying start fluid into your intake - it’s function is to help kick things off!

Not being an @rse just don’t want someone trying to work out why they’re not getting voltage to their CSI after cranking the starter.

Cheers