implications of disconnected O2 sensor?

[grahamkissack]

I'm doing my first valve adjustment and I noticed that the O2 sensor boot is disconnected from its hookup just next to the fuel filter. Judging by the dirt inside the sensors boot, it looks like its been that way for a while. What are the implications of leaving it this way?

Thanks, Graham

ps I have a 1980 sc

[911nut]

The O2 sensor feeds a low voltage signal to a controller under the passenger's seat. The controller interpets the signal as % CO and varies the duty cycle of the frequency valve on the K-Jet. This in turn varies the fuel pressure in the lower chamber of the fuel distributor so that the engine is running at 14.7/1 air/fuel ratio at all times except start-up and WOT. When the engine is at 14.7/1 the cat can do it's job of cleaning up the exhaust and fuel milage is maxed.
If you want maximum torque you would disconnect the O2 sensor. When you do this the system runs "open loop", like it does when the engine is cold. You can then manually set the idle mixture to 3-3.5% CO (approximately 12.5/1 air/fuel ratio). Acceleration is greatly improved as well as idle and part throttle operation (no "galloping" when going slow). The only downside, besides increased emissions, is poorer fuel milage.

[magic930]

When I first bought my car the O2 system was disconnected via the large plug under the drivers seat. When I reconnected it I had to lean out the mixture with the CIS head allen key adjustment. Gas mileage improved from 10 to 14mpg and the car actually ran a lot bettet in the lower rpm range, I probably lost a little power at the top end but the car was still fast enough to get to work everyday!

[nhromyak]

If you run richer (no O2), you can burn-up or clog your catalytic converter...

[Doug Zielke]

Originally posted by magic930
When I first bought my car the O2 system was disconnected via the large plug under the drivers seat.

This is not the same as disconnecting the O2 sensor (at the sensor, that is). The Lambda computer (under the pass. seat) must remain connected so the frequency valve stays functional.
Otherwise, the car will run like crap. Most O2-equipped CIS cars run better with the O2 sensor un-plugged.