Oxy Sensor??

While working under the lid of my SC's engine compartment,(in preparation for the tensioner upgrade), I discovered the wire from the Oxy sensor is unplugged (by previous owner??). Now, as a new owner, I'm puzzled as the car starts and runs very well. I have heard that if the sensor is disconnected the engine will run rich, but mine seems to run perfectly.
It also had good numbers in a recent emissions test.
Any suggestions?

Regards,
Doug
'81SC

Mine was unplugged when I bought my 83 SC. Runs ok with it unplugged. No sniffer laws here yet. Plugged it in and the idle hunts +/- 300 rpm. So I unplugged it again. It seems a bit rich when I first startup, but I think that is a good thing, keep the airbox in one piece maybe.

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Robert Stoll
83 SC
83 944

Mine too is unplugged on 81 SC. It is my understanding that this is a quick fix for a hunting idle, but typically isn't the cause for the hunting idle. I think I have narrowed mine down to a vacuum leak, as there is no line going to the vacuum port on the deceleration valve. I plan to trace the lines on the throttle body tomorrow.
Thanks,
Daniel

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Daniel Tisserand
1981 SC

On the way home from watching Tyson change my shift bushings (thanks Tyson), my car stumbled. A few times. Especially when accelerating from lower rpms. Scared me.

got home and looked at the OXS duty cycle which was very high. 58. I remembered tyson saying, earlier today, that in this situation the OXS system goes 'closed loop' or something. Anyway, apparently the OXS quits corecting the mixture under full load, and my mixture (58) was too (lean/rich) (shoudl be 45), so it stumbled. The rest of the time the OXS system was correcting the mixture, or at least trying.

I don't know why the mixture changed so much. But the adjustment returned much of the good performance I thought was missing.

As for the OXS, apparently your car will run fine without it as long as your mixture is set right. I leave mine plugged in. The correct the mixture and I'm not sure they run better without them, though some say they do.

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'83 SC

If your mixture is set correctly the O2 sensor on K-Jetronic FI in the SC functions only to operate the frequency valve. This valve functions to modulate the fuel pressure so that the car would meet emissions requirements imposed in 1980. Disconnecting the o2 provides a more stable fuel pressure and therefore better performance and drivability, esp in idle stability. It will also cool off the engine temp at idle as the car will be less starved for fuel at low RPM's.
Hope this helps.
Nick.

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Nick Shumaker
1982 911SC Coupe

If you are having better luck with your O2 unplugged, you might consider replacing it. I do not know if the SC use a one, two, or three (heated) wire O2, however, I can offer a bit of insight: An O2 sensor is an O2 sensor so long as the replacement has the same number of wires. My Turbo Buick had a single wire O2 and it cost about $35 to replace. My 88 944 Turbo had a three wire O2 and it cost almost $250 (i think - been a while) Anywho, looking at the sensor for the 944 Turbo, I noticed it was the EXACT SAME three wire as I have seen on the Ford trucks, the only difference being the connector that plugs the sensor to the harness. Being the kind that loves to foil retail gimmicks at every opportunity, I bought a three wire FORD O2 sensor, cut off the connector, removed my old 944 sensor and cut off its connector and spliced it on the FORD O2. The car ran great for more than a year of hard driving like that.

The point here is: don't let cost keep you from upgrading your O2 sensor. They do a pretty darn good job of keeping fuel consumption in check and when in good condition will keep your car running happily for many miles.

The early SCs did not have O2 sensors but the later SCs did. Mine has one wire, I believe.

Really, the way to deal with CIS is to go through the proper adjustment procedures and, if there's trouble, go through the troubleshooting steps. Of course, this sometimes involves a fuel pressure gauge, hoses and valve, or other testing equipment, but they're too terribly expensive. You find the faulty component and either replace it (usually) or repair it. Problems are actually rare with these systems and if everything is running properly, they start and run great at all temperatures.

Of course there are mysterious idle problems and the O2 debate. My O2 is connected.

Oh, and during warmup, the O2 sensor is not working, and the 'basic' mixture you set will control the mixture during this time, without those O2 sensor signals fluctuating. So idle problems during this stage are not the fault of the O2 sensor or frequency valve. They are more likely related to the airflow sensor plate, warm up regulator, auxilliary air valve or possibly the decel valve. My decel valve has been rendered inoperable and I do not have idle problems.

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'83 SC

I've been running WITHOUT my o2 sensor for about 5000 miles.My mechanic suggested unplugging it for better performance.He adjusted my fuel/air mix using a exhaust gas analyzer and assured me that this would meet ANY state inspection ! I have to say my car never ran better and my gas mileage has not changed.It is my opinion that the 3.0 engine
properly tuned will preform better without the o2.

Well, I am still having trouble getting mine off the pipe. Seems the socket just won't turn it. Thinking of applying some heat. Now that there is only three sides left on the original O2.