Need CIS advice
 

My 82 SC just failed emission testing:(
Everything but the CO was fine. The CO registered 2.49 and needs to be below 1.71 during the driving test. At idle it is 0.51 which is high apparently.
There are no Porsche experienced repair places anywhere nearby and my insurance runs out today!
Can I correct this by adjusting the CO at the fuel distributor?

I am too used to messing with carbs....

What tools do you have? Pressure gauges? CO sniffer?

I do have pressure guages but no sniffer.

I'm assuming you have a CO tester you can use to monitor as you adjust? Also, is your Lambda system working, and was your engine good and warm? What about your ignition timing, is that in spec.

If you Lambda is "working", I would pull the O2 sensor and clean it or replace it. I can't vouch for this method, but somebody else in here said "Heat it with a blowtorch then dunk in water to break up the carbon - repeat until clean." Me, I'd just replace if its that bad. They aren't too pricy.

If all those things are good, there's an adjustment on the fuel distributor. Unfortunatly I think the 82s have a "factory seal" that can't be easily removed with the unit in the car (you have to drill). If yours has already been removed, the hole is on the left side of the unit (next to the rubber boot) and takes a 3mm hex key. Clockwise is rich, CCW is lean, make small adjustments, and only mess with it when the engine is fully warmed up. Unfortunatly, the Lambda system is supposed to control the emissions at idle & part throttle... so it may counter-act your corrections based on sensor readings. You may also have to adjust the idle which is a big flat-head screw on the driver's side of the black boot.

Final option is to disconnect the O2 sensor in the exhaust. This will force the lamba into open loop mode, which runs rich (startup & high load when lambda is working). DO NOT just disconnect the Lambda system as this will result in the system running very lean.

With the system in open loop, you should be able to adjust the CO to acceptable levels w/o the lambda interfering. After you pass I would put everything back the way you had it to start.

Good luck

Many thanks for that Chris. I am thinking that since the idle CO is so high it may be 'carrying over' into the running mode....?

Hello David,

Is your car a US version or ROW ?

CO is directly related to mixture and you should be able to lower it by leaning out the mixture screw in the FD. If you have a US 911SC with CIS lambda, you can hook up an analog dwell meter to the test connector and read the FV duty cycle which is a proxy for the mixture adjustment. It is much better than making blind adjustments. Search this site for "CIS lambda" and you should find everything you need to know to about reading the duty cycle and the factory spec adjustment. If you have never adjusted the mixture on a CIS car, make tiny adjustments and drive the car between them. My favorite tool for this is a straightened allen wrench in a 1/4 drive ratchet. The CO spec for a US car is 0.4-0.8% at idle, but this is measured before the cat and cannot be related to an after cat reading. If the duty cycle is correct at the factory spec and you still have a CO problem, there are other issues to address.

02
 

David, you need to check your o2 system, is the frequency valve buzzing? is the relay under the pass seat clicking when you turn your key to run position? you can get a Bosch 1 wire 02 at oreilly's for 20 bucks. usually the relay and 02 are both kaput. You must use the bosche metel cased relay, the 5 pin plastic aftermarkets look the same, but they are not and will not work more than a few days..(the 02 relay get pretty warm) You can set your co with a dwell meter on an 02 car (get one at most parts stores for around 50.00) Most service manuals will explain the proceeder, good luck

what paul said to

She passed!!

I adjusted the CO screw two clicks CCW and decided to chance it. The change was dramatic! Every reading came down a lot.

Many thanks to all who helped :)

Now re-set it to make drive at it's 'optimum'. ;)

What he said :)

i was gonna suggest removing the oil filler cap, might let enough air to lean it out, then put it back on when done.

you might consider buying an LM1 since it is a regular thing