DIY Videos: How To Adjust Fuel Mixture on Porsche 911 Bosch CIS K-Jetronic Fuel Injection
Here is a pair of videos explaining how to adjust your fuel mixture on nearly every normally aspirated Porsche 911 running CIS.
Note: The following information is for educational use only. Before proceeding please read my disclaimer page.
Here is a short but sweet 2-part video series on how to adjust your NA 911’s CIS fuel mixture, whether you have the Lambda system or not. I have not had the privilege of working on any 930s or 965s so I cant speak for the details of the turbo CIS system.
The first one covers the open loop tuning to get you in the ballpark of a fuel mixture where the engine is happy. This ends up being the complete procedure for all US 911s 1973.5-1977 since those cars are open loop. From my understanding the ROW (non-US) cars through 1983 were also open loop so this applies to those too.
This first video is the first half of the adjustment procedure for US 911s 1978-1983 (equipped with the Lambda closed loop system with O2 sensor). You simply perform the test with the O2 sensor unplugged.
The second one is exclusively for US 911s 1978-1983, with the Lambda closed loop system and the O2 sensor connected to the system. The reason for this process is that the Lambda system can only adjust fuel mixture through a very narrow range, so you need to manually adjust the system using the first video, to get the mixture into a range where the O2 sensor & Lambda can then adjust the mixture on its own, then use the second video to fine tune the mixture even more. The end result is that the Lambda will take care of the rest and you should end up with an easy cold start, warm up, warm start and overall well running system.
Thanks to the direction of the Pelican forum Elders, I followed this procedure on my own car and have had a great running SC for several years now, at sea level or high up in the canyons, regardless of the weather. I wanted to have a lot of validation miles on the car before sharing it with others, but now I feel pretty confident that if you have followed all my prior CIS prerequisites and the methods above, you will also have a very strong chance of success. Good luck!