1983 911 SC mixture adjustment

[jbandbj914]

I have been told that the CIS system on my 1983 SC is sealed and you can not adjust the fuel mixture. Is this true? My 911 seems to be running rich.
Thanks,
Jeff

[scotricker]

Well you can adjust it. But there are different opinions on this forum regarding IF you should adjust it. It seems the best opinion is to have it checked at a shop with an exhaust gas analyzer while the adjustment is being made.

It takes a 4 inch, 3mm allen wrench to poke down into a secret hole that you almost can't see, to adjust a screw that you really can't see.

So I did it. It wasn't that hard afterall. If you have a Bentley Manual, look at the picture on page 240-8 for an idea of what this will be all about. I leaned mine a little bit. Probably should have it checked at a real shop someday. But now I know how to make the adjustment if I ever get onto the analyzer machine.

Hope this helps,

[boyt911sc]

Originally Posted by jbandbj914

I have been told that the CIS system on my 1983 SC is sealed and you can not adjust the fuel mixture. Is this true? My 911 seems to be running rich.
Thanks,
Jeff

Jeff,

The air mixture adjusting screw access hole is plugged to prevent people from tampering this factory setting. Specially from people that are not equipped to do the test. Removing the plug would give you access to the set screw (mixture screw) and be able to change the original setting.

Before attempting to change/alter the air mixture setting, check your fuel pressures first. And have a reading of your exhaust gas (by using a gas analyzer). Avoid quess-work and it would make CIS troubleshooting very easy and simple. Is the FV (frequency valve) operating while the FP is running? Keep us posted.

Tony

[Flat6pac]

You have to disconnect the ox sensor on the left side sheet metal or the lambda will recorrect everything you try to change.
Bruce