This is a CIS engine. If your engine looks like this, then someone swapped the 3.0 (or heaven forbid a 2.7) into the 1984.

http://forums.pelicanparts.com/uploa...1148320940.jpg

Re: .
 

I agree. (Except for the emissions test when that comes arround.)

I was quite educated on my ROW 83 CIS. I even did a little tweeking while barrowing an LM1 from a friend. This was a k-basic system without the O2 sensor, control unit, and frequency valve.

Except for in the warm up period (Control pressure lowered)
The mixture is varied, based on air volume, and the 3 different angles in the cone of the air flow meter. In the idle range, the shape of the cone is almost verticle, It then flattens out and near the top it get's steeper again. In addition to this the Control pressure regulator reduced control pressure as manifold pressure increased (Vacuume drops when you mash the go pedal).

When watching the LM1 you could see the mixture changing in relation to these features doing their thing. I have to believe that the initial idle mixture adjustment has an effect on the mixture in the "higher than idle" air flow.

What I saw is the mixture was arround 14:1 at Idle, then leaned quite a bit at light crusing and ramped significantly richer as the rpm increased the air flow and the plate was in that upper (steep) area of the cone. (I recall that that started in the 4000-4500 rpm range and the mixture got as rich as 10-1 near 6000-6500.

Besides those few days I never had the oppertunity to tweek the system further. (I'm not sure it needed it and maybe it was designed to do juat what I saw.) I guess I could have tweeked the system pressure and warm control pressure so that the idle was not too lean while the high end was not too rich. I'm thinking that if I raised the control pressure a bit I could have found that sweet spot.

Now this system was not as sofistocated as the lambda control, but I'm sure Porsche knew that and continued to tweek (hopefully improvements for performance) the k-basic system in the ROW cars until 84 with the Montronic cars.

So, I'm wondering if the basic setting is just as important in these upper rpm / air flow ranges on the lambda cars?

.
 

The pictured air intake is totally different. Ours has an air box with a square shaped air filter that lays right across the opening. The ?distributer? sits on top of that, and the hex slot is right next to the ?distributer?.. I can't really describe it better right now. I may be wrong on the year of the car too. I'll look at it when I get home.

The last picture I posted is the CIS induction with the airbox cover installed. There is a rectangular air filter that fits under that cover (the plactic cover with snorkle on the end of it).

I suggest that you and your father do a little more research into this before you adjust anything else. Folks who do not understand CIS or any other induction generally create more problems for themselves when they start to adjust things without understanding the effects of that action.

Sorry I was looking at the first one you posted souk.. The second one is the one ours looks like :)

OK. So you have a CIS engine.

Now read this thread:

http://forums.pelicanparts.com/showthread.php?s=&threadid=185926&perpage=20&highl ight=cis%20mixture%20idle&pagenumber=1

Bill:
Interesting observations. If you set it too rich at idle to compensate for different O2's at higher RPM's, the Lambda system will star too hunt.
Macel:
There are differences between SC engines. Some have Lambda.
What is the engine number?
You'll find it on the bottom of the fan post stamped on the engine case.
Use a light to find it. Something like 930/07 or 930/16.
We can help you undo the damage.
What year? What engine number?

Alright Souk, its been awhile, but I feel the need for one of my cars to trun a wheel. I'll be using all of your references/info to get my purple 72T running shortly I hope. I have flushed the lines and put a cleaner tank in it. It ran a little when I bought it a few years ago but wouldn't rev, coughing and sputtering. In retrospect that was probably due to bad gas as the tank look like the bottom of the ocean and the gas was red/brown filthy, heack it didn't even smell that much like fuel anymore so was probably a mix of fuel and water. Anyway, I am hopeful of getting it running since I seem to be taking 40 years to put the white E back onthe road.

By the way, I love Cat down here so it was a great move for me. Only bad thing is no Porsche content at all! They are laid back though, I've had the T sitting in the driveway since Nov. without headlights and never moving with no complaints or issues from the local authorities. I think where I used to live it would have been towed by now a few times!

Hey Dennis! Glad to see you post, and I'm very happy CAT worked out for you.

I'll keep a watch for your post/thread when you start digging into the car. Feel free to shoot me an e-mail directly too. I'm not ont he board as much these days.

I keep comming back to this thread from time to time. Great explaination how to adjust your CIS without all the proper tools available. I've seen a recent thread about the same subject but this one beats it by miles! I never adjusted my mixture going into winter temperatures and the car just didn't feel the same. Today I took the time to do the field adjust and it's running great now. As it should be!

Thanks for this write-up Souk!

"101 Projects for Your 911" MBI publishing, Wayne R. Dempsey 2001

Project 31, Page 95 Tuning and adjusting the CIS Fuel Injection - Maintenance and Adjustment, second Paragraph states: "The screw is indexed so that it should click when you rotate it. Turn it clockwise to richen the mixture, or counterclockwise to lean it out."

Mine doesn't click either, I thought something may have been removed or modified. Were some years screw indexed?

My 79 ROW is not endexed either.
It sure would be nice if it was.

I like the fact that mine isn't indexed. It allows for infinite adjustment. Anybody know how many clicks are in one revolution of an indexed system?

Unfortunately, every now and again there will be some bits of misinformation floating around that will get passed on as fact without having been first checked out. The mixture screws for the 911 air flow sensors have never been "indexed" to click as they are adjusted. Anyone adjusting a 911 CIS mixture screw and expecting to hear or feel a "click" will be disappointed.

I just assumed mine was worn out!;)
I wonder if the mixture on the MFI screws clicked?

OT:
Jim, have you ever come across part numbers for rebuild kits for Fuel distributers? Someone once told me he had a list, but after pestering the guy for a while, it was never produced. I wonder how they are obtained?

OOT: If you don't already know, I recently came across an area on the BOSCH site "Vehicle Part Finder" that listed their part numbers by application.

Bill,

I expect there are some experts here on the Forum who can answer this with more authority than I, but from my mis-adventures with adjusting the MFI pump some years back, I seem to remember clicks.

Re the fuel distributors, I have found that there are people who say there are rebuild kits available, but when asked for details, are unable to produce them. My findings are that there are authorized Bosch rebuilders who have access to the parts, but to them, this is proprietary info they won't share for fear it will impact their business.

Re the BOSCH part finder, I had a URL once that listed CIS parts, but can't seem to find it now. If you have such a URL, I would appreciate a link.

I've run into the same thing.
I did find a guy who has a Delorean SP? site that rebuilds several versions of the Bosch fuel distributer

I hope this link works!
There is some other interesting resources there as well.


http://http://www.boschautoparts.com/Resources/VehiclePartFinder/

I am reading this with interest but I need to adjust my idle speed as it is quite low ( 600rpm ) and sounds as if it is hunting...just a little, however when I put light pressure on the accelerator and bring it up to about 850'ish it sounds perfect. Can you please tell me how to find my adjustment screw. I have a 1983 911SC.

Thanks for any help.

jinxy

subscribed great work

The idle adjustment screw is on the front (front is the side towards the front of the car) of the throttle body. It is accessible from the left side. Without actually measuring it, it is about 1/2" in diameter with small "flutes" in the gripping surface so you can turn it by hand, alternatively, it also has a flat blade screwdriver slot. Turning counter-clockwise increases the airflow which increases the idle air bypassing the throttle plate, and increasing the idle speed.

Ok
Has anyone heard or tried to adjust with a digital VOM?

emac,

Are you thinking about a dwell meter? Those of us with points still use this outdated tool. If you do a search, you will find lots of info. I copied this off of Pelican a few years ago:

There is a test connector behind the plastic cover on the left side of the engine compartment. If you hook up an analog dwell meter to the pin with the green and white wire, you can see the FV duty cycle. The system is open loop when cold and the meter should show a steady 58 (65% duty). Once the engine is above 15C, the needle should start fluctuating between 40-58 in a steady rhythm. If the needle doesn't fluctuate you need to test the 02 sensor. If the needle fluctuates between 20-30, the mixture setting is too rich, between 60-70, too lean. When you set the mixture on this system, you are really only altering the open loop mixture (cold and WOT), the system corrects the mixture back within the range. I usually set it around 30-40, because I have found the WOT mixture too lean on many of these engines.

Rex

No I think I lost my last dwell meter about thirty years ago. Someone had posted something some months ago about using a DVM. I do remember something about hooking up to the oxy wire and ground but forgot where to set the meter. Anyway thanks for the info and time.

jinxy:
Like Jim says.
You also mention some hunting.
Idle speed and mixture are ajusted in conjunction.
To set the mixture, you'll need a LONG 3 mm Allen key.
Look for a small hole between the fuel distributor and the air sensor plate housing.
Set the approximate idle speed like Jim says, then insert the Allen key and fish for the small hex set-screw.
Turn very small amounts: Clockwise a little until the idle gets rough, then counter-clockwise until it gets rough again, then set it in the middle of the range.
Do not rev when the Allen key is in the set-screw.
It takes a little practice; do a search here on: "Mixture adjustment"; lots of info.
Of course, the shops use an exhaust gas analyzer to set the mixture instead of setting it by ear.
Your '83 may have a lead plug in the small hole. In that case you cannot adjust the mixture until the plug is drilled out.

I recommend that you get the Bentley SC Repair Manual.

Yep, found it and done the adjustment.It is idling at around 850rpm......sounds much better.

Thanks for that jim cheers.

jinxy.

Found this link in another post.

Go to downloads and click on the bosch cis link

Great read on the CIS SYSTEM




http://www.phat-gti.com

This is a great write up. Ok, if I understand correctly. Set my idle (4.5 Auto) at around 850. Richen - clockwise till rough then lean till rough while making note of how many turns. Then adjust clockwise 1/2 those amount of turns. Does this sound correct? Also, I did look in my WSM and my engine timing should be set to 31 degrees. My Harmonic Balancer shows 28 degrees, I set to a little higher than the mark. Am I in the ballpark?

You've got the general idea.
The whole movement is not even a full turn; a little cw, then ccw, then set it in the middle favouring slightly rich.

This is for Bosch K-Jetronic CIS in general terms; the optimum way is still with an exhaust analizer.

The ignition timing has to be done according to what the manufacturer calls for.
Like vacuum disconnected, RPM, Degree BTDC etc.
If the distributor hasn't been serviced for many years, consider doing it to make sure that it has the right curve.

My fellow 928 buddy and I went though the procedures on doing the ignition timing and then did the a/f adjusting. My rear brakes were apart while we did this, so we couldn't test drive. Sounds more responsive when blipping though. Thanks for the suggestions and I will let you all know of the outcome.

Sorry to ressurect this thread, but I'm trying to adjust the mix without a CO analyser...

However, I have trouble adjusting it with the car running. Whenever I touch the hex screw with the key, as carefully as I can, the engine splutters and dies...

Might indicate that he's close to one of the extremes (too low / too rich) ??

If I had to guess, it is running very lean. Downward pressure on the screw results in downward pressure on the air meter lever arm which also allows the fuel plunger to slide down in the fuel distributor.

If there is nothing else wrong with the car, you can turn the screw while the engine is off. Turn the idle screw 1/4 turn CW and it should richer it up a bit.

But! First ask yourself why you are so lean? The idle screw didn't move by itself so what went wrong to cause the mixture to change? Fix problems...don't compensate for them.

I was just wondering about turning it with the car running. With the engine off, I can adjust it and feel the results immediately.

Actually, I'm going through the mix after a series of prior fixes:
I had a blockage in the return line, after removing it, I had to re-adjust pressures as they were wrong to compensate for that. Now, that he pressures are right, I'm adjusting the mix.

Believe me, I already spent a lot of hours with CIS, if you cut corners, it will bite you.

Great advise........
 

Motosook,

I'm one of the many people who learned from your technique. I'm not sure if you added the above comment in your earlier posts because people tend to jump and tinker the mixture screw without realizing why the mixture changed in the first place. This mixture screw would not change its setting even if you wrecked the car!!!! Thanks.

Tony

Unfortunately, I cannot edit the firsdt post...the older posts are locked for what ever reason.

So hopefully folks will ready further than the first post.

good info

This just saved my 911sc. Bump as many people should be reminded of this thread after I spent days looking thru threads that just said "search"

There are two conflicting statements above. Anyone know which one is true?

(1) When you stamp on the gas, if you get a split second of hesitation before the car picks up, is this an indication of too rich.

(2) If you get a little hesitation when accelerating from a stop, like the engine is kind of "spooling up" before it pulls strongly, then the mixture is probably too lean.

I don't see a conflict. Split second and spooling up are two different things.

I am not saying either is right as I do not know.

Ok. Well, either way, my car isn't doing either!

I just didn't see the difference. Per another thread, I've got a 73.5 CIS 911 where I have the 75 911 WUR. I never had the vacuum line hooked up. But I'm going to do it shortly. This means my richness will need to be adjusted. So, I'm just reading up in anticipation of having to get it right again.

Actually, I have another question I don't see answered above. What is the usual range of adjustment between the two ends? I mean it says above to turn it CW until rough and CCW until cough, then set in the middle. So between the roughness and the cough, are we talking about 1/2 a turn, a full turn, more, less?

Thanks.