Well, I can agree with BoyT and Gunter but let us give Scott a break.

I am in the same situation and like to think that I have a very good understanding of the CIS system on my SC (thanks to the Pelicanites) and hard work.

If you would look up my posts you will see that I can not get my SC to run on his normal cold start routine as it should and a stumble at 2000 3000 rpm. It is all about finding the air leaks and as long as you do not have them all you can tune your way around it by setting the mixture until your blue in the face.

This is now almost two years. (admittingly I had it "fixed" so it was driveable)

I am now on my last effort to seal an air leak on the paper gaskets you find between the intake runners and the cilinder.

Where I do not agree with our CIS experts is that carb cleaner at an air leak always speeds up idle.
If your mixture is already rich the additional carb cleaner "floods" the cilinder or enginge causing lower revs and even a stall. That is what makes this CIS so difficult.
I even managed to have good driveabilty with a few air leaks albeit with detrimental effects to fuel comsumption.

Here is the thread to what I hope is my last air leak and what i believe is one of Scotts as well:

http://forums.pelicanparts.com/porsche-911-technical-forum/634135-intake-runner-gasket.html

You will see that it is possible on an SC to get the intake runners of with the engine in the car.

Good luck.

Michel

Vereeken - As noted on the last page I don't think there is a hard and fast rule. Sucking in the carb cleaner or starting fluid will change the idle.

I am not an expert. Tony and ossiblu teach me stuff daily. Gunter is a big CIS brain as well. These guys did not say the rpms increase.

Scott does need to identify and eliminate the air leaks with extreme prejudice. He is doing fine. Anyone who pulls the airbox and re-installs it is ok in my book. Everyone works at their own pace and method. Scott may be an artist and not a mechanical engineer. Frustration occurs because the posting participants actually care and want to help Scott fix his car.

I think the Tech discussions here are a 2-way street: Questions and answers.

Like a tennis match. If you don't return the ball, there is no game.

Unfortunately, Scott doesn't give clear feedback here about CIS or on his other thread about lowering the SC. I've asked repeatedly for some answers to indicate his knowledge about these issues without success, so, good bye and good luck.

Other people with similar problems want to learn when going through the posts.

What is anyone learning from this 10-page jumble? :(

Yes, a lot of DIY have no great technical skills but then why not listen to the experts? And have the courtesy to answer repeated questions?

BTW: As a general rule when looking for vac leaks, the idle will go up when introducing flammables provided the mixture is close to about normal, but.............I prefer propane, not carb cleaner.

Best..............and good luck. SmileWavy

Well lets wish Scott all the best.

I never had someone following my problem through 10 pages long ;o)

By the end of this weekend I will know if I have solved my last vacuum leak.

THe bottom line for me following my own problems and following Scotts is that CIS is often counter-intuitive and for a system with many parts that are not really interrelated it is not evident to understand what is going on somewhere else.

Michel

Like what for example...........
 

Michel,

Could you elaborate and help us understand that phrase? What CIS component/s in particular you are referring to? Or name one at least. Thanks.

Tony

The AAR and the Idle bypass valve.
I always assumed that the AAR passes unmetered air. Then after seeing the piping in the back an the airbox I noticed that the air passing through the AAR is flitered air that has gone by the plate. So metered. I still do not understand why this air in the AAR is metered air. I thought that was of no consequence at startup as the WUR is then set at overly rich.

The decel valve is another one. I have a decel valve that you can tune but it seems that when you screw it out completely it seems to hold the membrane slightly open and passes metered air again in the runners. If this is a problem or by design I do not know. In any case it took me a while to figure out that my decel valve was working OK as long as I did not exaggerate the adjustment.

The thermo time valve is another one It enriches my mixture when closed and leans it out when open. I find that counter intuitive. Even more strange - i have tested a couple and they all seem to go from closed to fully open anywhere between 10 seconds and max 45 seconds (after I had put it in the freezer). If you know that my LM 1 for measuring AFR takes about 30 seconds to heat up you can understand that actually could not telll the difference of AFR between startup and the time the valve opened. The valve was already open before the LM1 came on and it get s even worse when you gave it two or three starts in a row.

So I agree that CIS is no rocket science but it surely is not the easiest of systems.

Anyway, I learerd alot from reading your, Gunters, PaulPorsche etcs posts. But it was no easy sailing. And I still have to prove that I found my last airleak this weekend when I reinstall.

I think that back in the eighties a lot of mechanics must have been relieved when they saw the Carrera coming :o) only to get depressed again 5 years later when the first ECU systems started to fail :D

On a more serious note. Not far from where I live I have a big BOsCH authorized re-seller. They had some knowledge left of CIS but it walked out of the door when the guy took his pension. That is 5 years ago.:eek:
I have never found anyone since that day with a thourough understanding of CIS.

Michel AKA "Leakhunter".

You are going to get a ***** storm back from Tony. I ain't touching this one.

On the lighter side, I have a friend from Belgium that calls Heinekin beer "piss water". And he is serious. You guys must have some serious good beer.

He also turned me on to Belgian fries. After making a couple of batches with cooking oil, I looked it up on the internet and found that they (you) made the fries out of horse fat. I said to him, "They used to make the fries out of horse fat in Belgium" He said "What do you mean used to, we still do." Sweet.

Heineken is lemonade.

Michel

I do see that Gunter did says the RPMs increased. It is of no issue. idle changes

Gunter came and went. Tony is close to his limit and Scott is nowhere to be found.

Looks like I am the fool.

No, I appreciate all the help Ive received from you guys, Ive checked a lot of things, learned a lot. I dont want to bother you all anymore, so I think Ill just try to figure it out the rest of the way.
you guys have taught me a lot about this system
thanks again,
-scott

Decrease/Increase. Whatever it is, let us agree that vacuum leaks on a CIS alter the normal idle setting and trow off the AFR ratio at load further up the rpm range.

So vacuum leaks are the CIS worst enemy for sure.

I can confirm that I replaced my gaskets and rubber boots this weekend on the left cilinder bank (with the engine in the car) and that my warm-up routine has now improved.

When I start, it stumbles slightly then hunts at idle and then goes to 1.100/1200rpm and comes down ever so gently when warming up.

I have yet to confirm but I believe this is typical for a too rich situation -which makes sense as I adjusted my mixture to compensate for the air leaks in the system.

I am hoping that when I take the car out and warm up completely I can then set the co setting to the desired range.

I am hoping that my warmup routine will be better the next morning.

Then it is on to the right cilinder bank (but I am less motivated as this seems more difficult.

Michel

I just found a couple of leaks using the Tony method. Guess what? Idle slightly surged from being too rich. I have the luxury of the O2 system and the dwell meter test port. Dialed it right back in.

Clockwise = richen. Always end your adjustment with a clockwise turn even if you are leaning out. There are good threads and I think Sokus (and others) have a good method for setting pretty close w/o an exhaust sniffer.

Where in nor cal are you located?

Speaking of the test port ... I wish someone would post images of how to connect the dwell meter to the test port.

I tried it once and got shocked to hell when the contacts touched. The space is awfully tight for the alligator clips that came on my meter. After that experience, I never tried again but I'd give it another go if I could see some close-up pics.

Do any images of the proper connections exist?

I will get some pics directly. Pretty easy setup

MCA - Here are the connections and a quick rundown on what I do. I have never been shocked by the test ports and never have seen sparks when making connections - and I have pretty fat fingers.

This is a little off topic but Scott can use this (3mm wrench) data when he gets to the point of manually adjusting his CO without a dwell meter.

All, please criticize or confirm steps taken. I only know what I know and if I am doing something wrong, let's get it straight now. The car was "warmed up" in the garage for 15 minutes for this exhibit. I think a nice 1/2 hour drive would be a better starting point.

Green wire
http://forums.pelicanparts.com/uploa...1318979746.jpg

Dwell meter connected to green wire test pin

http://forums.pelicanparts.com/uploa...1318979860.jpg

Dwell meter ground connection

http://forums.pelicanparts.com/uploa...1318979918.jpg

Modified 3mm allen wrench (and larger allen wrench that drives bolt and fits above metal fuel lines)

http://forums.pelicanparts.com/uploa...1318980101.jpg

Wrench in place - note hand placement so you can use your thumb and index finger to make sure it engages with the air sensor screw

http://forums.pelicanparts.com/uploa...1318980306.jpg

On first startup, needle remained at 20 (40 with 8 cyl reading doubled)

http://forums.pelicanparts.com/uploa...1318980481.jpg

When idle started dropping (minute or so) , needle started dithering and dropped all the way to 10 plus or minus on the 8 cyl scale.

http://forums.pelicanparts.com/uploa...1318980642.jpg

As it warmed up the needle climbed almost to 20 (40 if 4 cyl scale) but then stopped. Odd, because I had just set it last week and it was at 45+-. Then I remembered my WUR electric connection does not have the metal retaining wire and it consequently vibrates off. I plug it onto the WUR connection and watch it climb from 20 to 30 (40 to 60) in about 10 seconds. Now I am lean and I know my adjustment the other day was off because I did not have the benefit of the WUR being completely "off" from the cold control pressure mode. I adjusted the other day with more WUR leaning out still remaining.

http://forums.pelicanparts.com/uploa...1318981098.jpg

I turn clockwise the 3mm wrench and get it close to spec. Note these are the before and after pics - not real clear because of camera angles - but you can see that the wrench turned very little to richen it to the 45 +- range (4 cyl scale). Maybe 1/30th of a turn.

Before:

http://forums.pelicanparts.com/uploa...1318981717.jpg

After:

http://forums.pelicanparts.com/uploa...1318981802.jpg

Here is a youtube video I made to show the dithering. The range is slightly lean - on the fat side of 45 - but better than it was.

K Jetronic with Lambda Dwell meter dithering - YouTube

Bob,

Thanks a ton. You couldn't have made it more clear. Perfecto.

For some reason I thought both alligator clips connected at the test port - one to the green and one to the brown. Hence the touching. Yea I'm an idiot.

I'm always hesitant when it comes to electrical stuff. The most I've done from an electrical standpoint is rig the fuel pump jumper for pressure tests and changed my headlights to H4s (added relay). I have no problems digging into the engine, but electrical issues scare the crap out of me. I need to pick up a good book in order to gain a broad overview of how it works - especially reading diagrams. If you have a book suggestion, please let me know.

Fortunately my car is running tip top at the moment. I replaced a bunch of CIS stuff during my rebuild. But if I run into CIS issues down the road, this will be one of the first tests I perform. Might go ahead and give it a try this weekend for grins.

Thanks again. Huge help and a great tutorial for everyone.

Cheers,
Craig

Here are my Elgin 964 cams that I have had for years - on the shelf for my 81.

I think we can do a little bartering. Electrical diagram help for some 964 cam insight.

PM me your e-mail and I will show you the garage-wall SC diagram for dummies. It is sweet.

Cheers.

http://forums.pelicanparts.com/uploa...1318988862.jpg

Hey guys, thanks for all the help, after sealing airbox leaks that i found with carb cleaner and tightening that last nut down, i finally got the thing in pretty decent running shape. it idles well at 1k rpms with the throttle speed screw turned out somewhere around 1 turn, i think. it feels pretty good anyways

-scott

Bob, I am at this point now, and I was just wondering, without a dwell meter, is adjusting the air fuel ratio even doable, or do you really need a meter to measure the exhaust content to get it right?
thanks
scott

to be quite honest, even though there is a picture showing th screw location, I am struggling to find it