CIS Update!!

Good morning everyone!!!!!!

For those of you who have been following my saga, and kind enough to chime in, I have another update on my progress with my CIS system.

Yesterday, I did my best to adjust the sensor plate height, but I found it very difficult to determine the proper adjustment. Peering down into the venturi with the boot partially removed, finding the optimal height is pretty much a "guestimate." I gave it my best shot, and then moved on. By the way, the venturi and sensor plate were squeaky clean.

Next, I let the engine come up to operating temperature, and proceeded to "set" the mixuture and idle settings. I spent nearly an hour, going back and forth between the idle and mixture adjustments before arriving at what I believe is the best adjustment I could obtain by ear/feel.

Through all of these adjustments, and even with my final one, there is a roughness in the engine performance in the 2,000rpm to 3,000rpm range. Despite all of my adjustments, I was never able to get this rectified.

This morning, I started the engine from dead cold, monitoring the control pressure, and here are the results:

1. The car started on the first try, struggled a little, then settled into an idle at around 1,000rpm's (where I set the idle last night). I did not get a fast idle for any period of time. The control pressure at start-up was around 2.5 Bar (35psi).
2. The engine ran for around 1 minute, at which time the control pressure had risen to just under 3.5 Bar (50psi), and then started struggling and surging. After a couple of rpm surges, it stalled.
3. I re-started the engine, and while it was struggling, quickly inserted my 3mm allen wrench in the mixture adjustment hole, and richened the mixture slightly, which got the engine idling fine. Control pressure maitained itself at just under 3.5 Bar (50psi).

I've spent hours upon hours of gathering and reading information (both from this BBS and other sources) to learn about this system, and based on this, I have the following comments and questions (remembering of course that I'm certainly not a Porsche mechanic, so correct me at any time!!):

1. It seems to me that I have a minor issue with either the Warm-Up Regulator (WUR), the Auxiliary Air Valve (AAV), or both. I feel the WUR may be coming up to warm operating control pressure to quickly, leaning out the mixuture to soon. It may also have an initial cold start pressure that is too high, again leaning out the mixuture too quickly.
2. Regarding the AAV, I'm not getting a fast idle at all. Doesn't the AAV function to allow a short period of fast idle? Can the AAV be tested? How? Can it be adjusted (it's certainly not easy to access)?
3. Without a gas analyzer and other tools, I could easily be way off on the timing and mixture adjustments. I could also be off on the sensor plate adjustment. Regardless, I believe I'm on the right track, however would it be wise to take the car in to have these things adjusted to spec before I make any changes to the WUR or AAV?

While I have your interest, I have a comment and question on a side item. With the car idling for some time while I was making the mixture adjusments, it started smoking quite a bit. It has smoked slightly at start-up in the past, but now is smoking quite badly when warm. The oil is not overfilled, and I seem to notice that this may have occured after the last oil change. When I bought the car, it did not smoke, and I've only put around 4,000 miles on it. Input?

Thanks everyone!!!!!!!!!!!!!!!!!

Michael,

How cold was it when you started the car? Was the cold control pressure within spec for that temperature?

There is a procedure for testing the Aux Air Valve. It's located on the side of the engine and is fairly easy to get to. It's item #36 in this diagram.

http://www.pelicanparts.com/911/911_Parts/1978-83/1-7-2.JPG

I have seen earlier threads on how to test and adjust the AAV.

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Bill Krause
'79 911SC Euro

Isn't the Auxilary Air Valve different from the Auxilary Air Regulator, which I *think* is part number 36?

I had thought that the AAV provides the "clean and reliable" air source during warmup, ending its effect when the car starts. The AAR, as I understand it, is the temp-controlled (via current) item that provides air to the underside of the throttle valve via a rotating disk. It closes as the current warms the internal arm such that it turns the disk and closes the (when cold) open hole.

Forgive any confusion I might add; my US '78 may be different?

Jw

Jdub, You're correct. I've seen those two devices called different things. I think the device that SeaDweller needs to look at next is item #36, not #39 (what ever they are called).

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Bill Krause
'79 911SC Euro

Because the CO adjustment is critical to good operation, I suggest you have the CO adjusted at a smog station when the car is at operating temperature. Then leave it alone and work on the other parts of the CIS system. I had to add a 5 ohm 5 watt resistor in the Warm-up regulator wiring so the regulator take a longer time to bring the idle down to normal. The car should idle at about 1200-1500 rpm at start-up and drop to 900-1000 rpm warm.

Ken

Bill,

It was around 60 degrees farenheit (16 celcius) this morning, and based on the pressure charts, the control pressure at cold start should be in the range of 1.8 to 2.3 bar. Mine seems to be out of this range at 2.5 bar.

If I adjust the WUR control pressure down to within the range indicated cold, will it change the warm setting as well? If I'm understanding things correctly, it seems that the warm control pressure is adjusted at the fuel distributor, so the cold and warm system pressures are adjusted independently, at different locations.

Jdub,

I believe you are correct about the AAR and AAV, and you raise an issue as well. Part #36 is called the Auxiliary Air Regulator, and part #39 is called the Auxiliary Air Valve. In reading information on some K-jetronic sites, I wonder if the AAR is being referred to as the AAV, and vice versa? I can find nothing that clearly explains the operation of these components as separate items, as it seems that AAV and AAR are used interchangeably.

Based on the diagrams, it looks like they work together in some way, however I don't know what each component contributes.

Can anyone clarify what the AAV and AAR do?

Thanks!

Michael

Micheal,

It is easy to remove and test the AAR part#36 (not AAV). Unplug the wire, loosen the two screws holding the the two hoses and remove the two bolts holding down the AAR. This takes 5minutes to do (I did it yesterday night).

Once out look though. It should be partially open. I don't know the specs for it (ie: how much it should be open for a given ambient temperature). Put it in the freezer for 30 min and it should go fully open. Then apply 12v to it and it should close. Mine takes almost 20minutes at 12v to close, and never really closes. I removed it because I have no high idle when cold, and suspected the AAR. I actually drilled out the rivets and had a look inside. I adjusted it so it was more open than before, but I may have gone too far as my idle is now 2500rpm cold. I have to take it out again....

I also drilled a hole in the exhaust and welded a bolt. Then bolted on an O2 sensor. I just use a volt meter to monitor the mixture.

Tony

Michael,

System pressure is adjusted by adding shims to the fuel distributor. Control pressure is adjusted by tapping the plug on the WUR. I think that adjustment does effect both the cold and warm control pressures. If you can't get them both within spec, it may be time to look for a rebuilt WUR. I've seen them available for around $80.



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Bill Krause
'79 911SC Euro

SeaDude:

The Bentley SC manual does a fair job of descibing how each item works for our 78/9s. If you give me an address, I will photocopy the material and send them to you.

Keeping in mind that I know next to nothing on this, let me try to paraphrase the manual. The AAV is intended to provide an alternate air flow on cranking the engine. When the engine starts, the AAV is *supposed* to shut off. How? By counter-pressure from a tube that pulls a diaphragm in the AAV shut that had been open by spring load. So, to restate, the spring pressure keeps the diaphragm open, car is started, and running engine vacuum causes diaphragm to shut closed. I suppose if this was not shutting, you would have a lean condition. Leon posted some time back how the "hunting" and "surging" *might* be tied to an AAV that would not stay closed shut, but rather bounces the diaphragm shut and open. I wonder why? Maybe a deteriorated diaphragm or insufficient vacuum from the engine that allows air to continue to bleed into the system.

And yes, looking at the Haynes Fig 11.17 for '79 models seems to show that the hose from the AAV to the engine proper is shared by the AAR, which is a bit downstream.

Like Tbitz, I took my AAR out for a peek and a dosing of WD-40, but stopped short of adjusting it, though that can be done. The purpose of this item is to continue to bleed air into the system during warmup, slowly closing off the air by way of a round disk with a hole in it. The hole is open when cold, somewhere between the two when warm, and then closed when hot (maybe it normally stays open a bit? unsure here). In all events, it is time-related as a current applied to a bimetallic arm attached to the disk cause the arm to move, the disk to turn, and the hole to close. Here again is an item that could easily be bleeding excess air into the system by way of not closing. If you do remove this item, do yourself a favor and slightly bevel the ends of the machine screws. I had a bear of a time trying to get the screws to start threading back in (A/C here, so YMMV). I did note the BEAUTIFUL job Porsche did to machine the area on which this item sits, and the reciprocal machining on the body of the AAR itself: they match up nicely for a, you bet, solid, heat-transferring mating surface. This tells me that Porsche intended ambient engine temp to have some sort of effect on this device.

Whoa, rambled long enough on this one! I'd say in general that if you are running lean it would be good voodoo to visegrip the hose going into the AAR (look for arrow on top of AAR for direction of flow) and the hose going out of the AAV, heading to the plenum.

Jw

One quick note. Both the AAR and the AAV provide bypass air around the throttle body, they don't bypass the sensor plate so neither one will affect the mixture, only the idle speed.

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Bill Krause
'79 911SC Euro

OK, I'm clear on the pressure adjustments now....Thanks!

I just spent another couple of hours on the engine, and I just can't get things dialed in. I believe without the right tools and test equipment, I'm flying blind.

I re-assessed the smoking issue, and it simply does not smell like oil burning, which has a distinct odor. I'm going back to my original thought that it is an extremely rich condition causing the smoke, as the smell of fuel is very, very strong. I've tried leaning out the mixture, but even leaning it out until the motor stalls still does not alleviate the smoking.

Having given it some thought, I think the WUR is close enough to spec that it isn't the culprit here. Sure, I could lower the cold system pressure a few PSI, but I don't think that will make a dramatic difference, although I could be wrong.

I'm beginning to wonder if the thermal time switch might be bad. If the cold start injector never stops operating, wouldn't that cause an extremely rich condition?

What puzzles me though is that richening the mixture helped this morning when it was struggling during cold start????????? Many of my findings are counterintuitive!!!!!

I thought I was making some headway, but without the proper test equipment, I may never get close enough for the engine to run properly. I'll fiddle with the car this weekend, but if I can't get it running right, there's a CIS guru 10 minutes from my house that I'm going to pay a visit to Monday morning. I had really hoped to lick this myself, and I'm glad I tried, because I'm no longer "afraid" of the engine and could probably teach a class on CIS!!! 8)

Once I get this worked out, I'll post the results for everyone. Perhaps it will help the other 99% of Porsche owners who seem to have this problem at one time or another!!!

Thanks!!!!!!

Michael

I apologize as this is gonna get long, but I really need some help here.

I finally got all the missing pieces to put the CIS back together correctly, I think.

I have a couple of questions for you folks that are months ahead of me:

Part 47 in the link (above in Bill's thread), Where does it connect? To the airbox?

I still have not figured out the mounting on the AAR part 36, the AAV part 39, or Thermovalve 17A. I am going to have to tap into the wiring harness to put these parts back in service as I can find no electircal connectors other than for the WUR.

Also it appears that the car was cofigured as a 75 year, without all the cold start hardware. The throttle body only has one port where hose 13 connects, the area where hose 5A connects is not even tapped for a port (Again 75 variety - I assume).

Can I make this work if I tee into the system to route the hoses? Or do I need the post 75 year throttle body or can I tap this prot to connect the hose 5A??

Does the AAR have to come in contact with the engine on the machined surface??

The first person with any good photos of this stuff in action gets a six pack of cold beer. (Brand Negotiable)

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78 3.0L/3.2L CIS 911SC

David, do yourself a favor and get the Bentley SC manual. The chapters on the CIS will answer many if not all of your questions. The book is notable particularly for the clear images of all the key parts and how they fit on the engine.

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Doug
'81 SC Coupe (aka: "Blue Bomber")
Canada West Region PCA
members.home.net/zielke/911SC.htm

I had to use both the diagram that Bill provided, in addition to one that I'll send you directly via e-mail. My application was a hybrid of the two, with a twist.

Basically, my throttle body only has one small vacuum port on the front, and one on the back. Because of this, the line going from the bottom connection on the Warm Up Regulator (#5 in the diagram I e-mailed to you), to the Thermovalve (#4 in the diagram I e-mailed to you), has a "T" in it, with the "T'd-off" line going to the vacuum retard on the distributor.

The diagram I e-mailed you also shows the connection of part #47 on Bill's diagram. If your Air Flow Sensor Boot (part #18 in Bill's diagram) doesn't have a port, I have an extra one that does.

As a point of clarification, part #5A on Bill's diagram is not a vacuum line, but a fuel injection line retainer assembly. To clarify the connection of the vacuum lines using Bill's diagram (if your set-up is like mine that is):

1. The vacuum line going from the top connection on the Warm Up Regulator (line #16, #17 and #13B on Bill's diagram, although I don't have item #17 in my system) goes directly to the vacuum port on the front of the throttle body.
2. Line #13 in Bill's diagram goes to the vacuum port on the back of the throttle body. Line #13C has a "T" in it, with a line going to the vacuum retard port on the distributor. Just so you know, it does matter which vacuum ports are used on the Thermovalve, even thought it appears there should be no difference, so make sure the lines are connected as shown in the diagrams.

Regarding the mountings, the Thermovalve and Auxiliary Air Valve are mounted on brackets, and the Auxiliary Air Regulator is mounted directly on the engine, under and just behind the right front intake runner. The Thermovalve's location is under the heater blower motor assembly, and the AAV is back behind the fuel distributor.

Don't forget to check your e-mail for the diagram, and good luck!!

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Michael
'78 911SC Euro

Hello

Just to make it clear:

It looks like you have the early CIS witch has less electric. Your Throttle body has a pressure actuator and your electric connections are simple spade connectors ?

Even on the WUR wich is much smaller then later units.

For a correct warm up these engines used the handthrottle.

Grüsse

Hello

This is how the early parts look:

http://www.pelicanparts.com/911/911_Parts/1974-75/2-3-1.JPG

[IMG] http://www.pelicanparts.com/911/911_Parts/1974-75/2-3-1.JPG [/IMG]


Grüsse

Roland,
Thanks for the help. I think Seadweller has me staightened out. My system is actually more like the later variety posted earlier in this thread with the exception that the throttle body has only one port and attached to it is part #20 as listed on the schematics you linked. All of the other components seem to be of the later variety. I'll probably be sorry I put all of this equipment back as original, but I have learned a great deal so far and I'm sure I am still on the steep part of the learning curve.
Thanks to all.

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78 3.0L/3.2L CIS 911SC