I've had the same thing on my 82 SC for a long time so I hope when "dano" finds his solution he will post it here so I can try that on mine first... (I live with it because I've got so many other things to fix that I haven't gotten into determining the cause yet though I'm certain it's in the fuel system).

I've also got 2 Bosch K-Jetronic manuals and the troubleshooting charts point thusly (and I quote, sorta - can't draw the charts here in text):

Poor idle - cold =
-Airflow sensor -or-
-Warm-up regulator -or-
-Cold start valve -or-
-Thermo-time switch -or-
-Auxiliary-air device -or-
-Pressure actuator -or-
-Throttle switch

Well, I guess that didn't help much, but it's better than replacing/testing everything, huh? http://www.pelicanparts.com/ultimate/wink.gif

More thoughts --- seems on further checking I actually have 4 Bosch K-Jetronic books (where did I get all this stuff? http://www.pelicanparts.com/ultimate/wink.gif )

A little reading leads me to believe that my problem on my 82 SC (which I think is identical to yours) points to the warmup regulator. The manual seems to indicate that the Cold Start in combination with the Thermo-time switch is really limited to only the first few seconds (maybe 10 or so --- it's not real clear on the length of time) of the startup period. Since mine and, I think, yours, starts instantly every time (mine does, no matter what the weather) but then coughs and spits for up to about 4 minutes afterward (depending on the weather) the manual seems to point to the warmup regulator as taking over during this period of time until the engine gets up to full operating temperature and warms up the walls of the intake tubes and cylinder walls so that the right fuel mixture now reaches the combustion chamber and everything runs right. The Warmup regulator also works in conjunction with the Auxiliary-air device (haven't looked in mine yet to see if I have on of these though I remember one on my 74).

Anyway, that's what I can offer without just copying the whole book in here (can't anyway, you know, copyrights being what they are and all ha ha http://www.pelicanparts.com/ultimate/smile.gif )

Good luck and let us all know what you find.

Hi, I found this topic using the search function and asked tog if he can list his
K-Jetronic books. Here is what he answered:


Robert,
OK, happy to oblige

1.
"Porsche Troubleshooting Guide K-Jetronic"
"Printed in Germany", "Copyright by Dr.Ing h.c.F. Porsche", "Printed by
Beck & Co.", "7000 Stuttgart 40", "02 / 1978"
5.5" x 9/5" about 50 pages?
No ISBN number that I could find... I must have gotten it from Porsche.
This is wall-to-wall flowchart book of how to troubleshoot problems... I
like this book. It does have some B&W pictures to clarify adjustments and
some good B&W diagrams.

2.
"Bosch Technical Instruction K-Jetronic"
"1974 Robert Bosch" "Printed in Germany" "2nd Edition September 1978"
8.5" x 11" about 30 pages
Again, unfortunately, no ISBN#. I also like this one... It has excellent
diagrams in color
and explains each of the pieces of the system and what each one does. This
definitely seems to be a classroom instruction book since it even has a
test at the back.

3.
"Bosch Fuel Injection & Fuel Management"
"By Charles O. Probst, SAE"
1991
This is a Robert Bentley, Inc. published book... didn't realize I had one
of the famous Bentley books!
ISBN 0-8376-0300-5
8.5" x 11" about 200 pages?
Top notch paperback with diagrams, B&W pictures. Covers ALL BOsch fuel
injection thru 1991 such as the LH- KE- Motronic, and LH- L- D- KE- K-
Jetronic

4.
"Solving Bosch CIS problems" By James Weber 1992
"Future Education, Automotive Division" "424 Lamar Blvd Ease Suite 102"
"Arlington, TX 76011"
Again, no ISBN#. This is for K- and Ke-Jetronic Theory, Diagnosis and
Repair... not too bad either though pictures and diagrams are a bit grainy.


Good luck on finding these. I bought them long ago and can't remember where
I got them. I like them all. Feel free to post this on Pelican if you
like... I haven't had much time to visit there in the last 2 months and
maybe someone else may find this useful.

TOG




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Robert / 80 Targa