How far open should AAV be?
 

I think I have a bad Aux Air Valve because of cold start issues. It's 90% closed at room temp (crecent moon with square notch). It doesn't seem to change when in the freezer. I haven't hooked it up to 12v yet.

How far open should it be at room temp? I have attached a pic.

Thanks.
Chris
http://forums.pelicanparts.com/uploa...1144180510.jpg

I just went down to my garage to check my spare, and it's about 65 deg currently my spare AAV is about 20% open. If I freeze it (from memory) it closes to all but say 2% open.

This Units are not Very presice . So be patiente and verify the opening and closing of it. If they stay open the Air Calibration is very hard. Get a New unit or if you have an extra unit verify the closing and opening

VicSmileWavy

http://forums.pelicanparts.com/uploa...1144183946.gif

I should also add that per another post here, I "upgraded" per say to the 17 ohm version from the 33 and it works much better.

That is the AAR(egulator) not the AAV(alve). If you search " mystery train" or "mysterytrain" you will see how he got this thing to work better.

Have you tried your revised unit on the car?

You're right. Sorry about that. I see lots of people calling it the AAV but didn't realize there was another part called that. I can't find AAV in the PET. Is that what's also called the vacuum limiter?

I had a previous thread on the same topic. It might answer some of your questions.

http://forums.pelicanparts.com/porsche-911-technical-forum/112138-aar-good-bad.html?highlight=aar

http://forums.pelicanparts.com/uploads/AAR123123123.jpg

Simon,

Tell us about the nut and bolt you added to the AAR. You were able to adjust the sensitivity with them?

I think I know where the AAV confusion started: the diagram in the Bentley book calls it an AAV. Adrian also reprinted this diagram.

Anyhow, I came how today and noticed that my AAR was closed farther than before. Sitting on my desk in the sun and it reaching 70 degrees here (about 85 in my home office) made a noticeable difference. I put it in the freezer for an hour. It was open about half way. I then baked it at 350 for about 15 minutes. Closed all the way. So I guess that's not my problem.

Thanks for the replies. I guess it's time for a fuel pressure tester.

Where are you at? you can borrow mine.

Yes Simon tell us how that works.

What problems are you having? Also, I don't think I saw what year your car is. You may be experiencing the typical WUR related problem of too high cold control pressure.

I'm near Denver. Thanks for the offer, but I think my AAR is fine.
My problem is this:
1) when stone cold, starts OK but a little rough. Takes some throttle to bring the idle up.
2) when warm, starts fine.
3) when sitting for more than an hour but less than the time it takes to be stone cold, will just turn and turn without firing. Sometimes it takes more than 30 seconds of turning to get it to fire. I haven't killed the battery getting it started, but I'm afraid that I will someday.

I have a 91 Turbo. I'm posting here because there's more people here with CIS than the 964 group.

1 could be the WUR/ccp. You should check the pressure. You may be able to simply knock the plug in to get it correct.

3 sounds like either the fuel accumulator or check valve. Lots of info on this via a search.

Do you know where to find the check valve on a 91 Turbo? I'm guessing it's somewhere in between the rear pump and accumulator but I haven't dug in to find the rear pump.

I believe the check valve is located on the front fuel pump. Same as earlier 930's. The front fuel pump is located behind the front suspension pan. A real treat to get to.

loot

The Valve is part # 911 608 211 00 or valve # 893 906 093

VicSmileWavy

http://forums.pelicanparts.com/uploa...1144330402.gif

Thanks. I found it in the PET after much looking. It calls it the "retaining valve".

Paul is correct you need to look at your pressures. Th AAR is Porsche's lame attempt at an automatic throttle device during warm up. The larger the opening when cold the faster the engine will idle. The important thing is that it closes completely and seals the opening once the car has warmed up. If the AAR is leaking then your idle will be high and then folks start to screw with the mixture and idle speed and things way out of whack.

Ok Gurus
If you have to turn your Air Mixture Screw in the Trottle Boby almost to the close position it might be indicative that one of your CIS componets is leaking( Vacum Leak) that is .

VicSmileWavy

http://forums.pelicanparts.com/uploa...1144333233.gif

Hey Guys I was just cheking a spare AAR and apply some 12v for a few minutes and I just notice that after complitly closed, it still let some Vacum in.
Then I just took out others (AAR) that I have for spares and I noticed that some of them restrict more vacum that others. They supposed to close all the way and restrict or shot the Vacum ?Or are they defective?

Vic
SmileWavy

http://forums.pelicanparts.com/uploa...1144884485.gif

loot87, your symptoms sound familiar. Check out this thread:

http://forums.pelicanparts.com/porsche-911-technical-forum/275616-cis-hard-cold-start-if-youve-ever-had-problem-please-read.html

All AARs are not created equally. Some remain partially open when warm resulting in mixture and idle tuning done to compensate for the continuous vacuum leak. I have removed the AAV and the AAR on my engine and have tuned appropriately for it.

You can easily determine if you have a check valve or fuel accumulator problem. Unplug the electrical connections to your WUR and AAR. Turn on your fuel pumps for 1 minute to fully pressurize the system. Hit the key. If the car starts as it should you have a leak down issue.

i had the same symptoms. sitting for a spell after driving, it would be a beotch to start. i checked my CIS pressure and i found my at rest pressure going down fast. one of the test is to find the source of the leakdown. the first move is to build the pressure up again, and shut the car off. when the pressure takes a dive, you shut off the valve on the pressure tester. if the pressure holds steady, then it is leaking down thru the WUR. which was my case. new WUR and all my issues went away. the key is to test the pressures.

My pressures are dropping pretty quicky after about 10 minutes. The line to the WUR is closed. I replaced the check valve and nothing changed. So what's next, the accumulator?

What is your system pressure?
What is your pressure after 10 minutes?
What is your pressure after 12 hours?
What line is closed off on the WUR?

System pressure is 7.
Control pressure is 4.5 with 85 degrees ambient.
Pressure after 9 minutes was 1.4.
Pressure after 10 minutes was 0.
The tester line to WUR is closed so I am just reading the pressure from the dist.

I had a condition just like that, in fact it leaked a bit quicker. It turned out to be a leaking fuel injector that was draining into the cylinder.

You can actually test pretty easy for this by getting a few small jars and just letting the injectors sit in them after the pressure test.

Pressure after 10 minutes was 0.

Looks like we know what the problem is. The engine will flood if you have injectors leaking down. If that is not the case I'd look at the accumulator next. There is a diaphragm at the bottom that can rupture resulting in loss of system pressure. Does your accumulator have 2 outlets on one end and 1 on the other? If so you can pull the bottom return line. If memory serves fuel will spill out if the diaphragm has ruptured. A schematic of that unit should show this. I can't look now but will try to find one a little later.

Thanks for your help Rarly. When the engine is warm, it just turns over for about 30 seconds to a minute before it fires. How can I tell if it's flooded?
I'll take a look at the accum and see if it exhibits the behavior you are talking about.

Thanks Scott. I'll also test the injectors.

If it takes approx. 30 sec. for the engine to start, it usually points the fuel accumulator or the check valve located on the front fuel pump. It takes a while to pressurize the system when it is fully discharged. Also check for any leaks in the line that could cause the system to lose pressure. It doesn't take much.
If your exhaust is really sooty after turning over for 30 secs and then starting, it's not a loss of pressure that is causing your problem.

I replaced the accumulator over the weekend and now the residual system pressure stays at 2 bars for 30 minutes. Cold start is much stronger than before but it just started snowing here, so I'll have to wait a day to check the warm-start to see if I fixed it. I think I did.
Thanks to all for the help. I wish I had resources like this 15 years ago when I was trying to fix my 68 Mercedes 200D (blown head gasket after 400k miles).