O2 Sensor
 

In the continuing saga of trying to determine why my car is shooting black smoke I found that the O2 sensor has been disconnected and the male part of the plug going down to the sensor has been completely cut out at the grommet where it goes outside of the engine bay.

Why would this be disconnected (and cut out) on an 87 Targa? I understand the earlier SC's benefitted from disconnecting the O2 sensor, but how about and 87 Carrera?

Thanks,
Michael
87 Targa

I have no idea why, but I found the same thing on my 1986 coupe. When I reconnected it, the idle came down from 1,000 rpm to about 850 and the gas mileage improved. I did not see any "down" side.
Paul

On Pulsed injection systems such as the 84 and later Carrera you MUST have a connected and working O2 sensor. Without it the car will not run correctly. I would say making sure yours is connected and working is a starting point.

The disconnection only is OK on the K-Lambda CIS system on 80-83 USA 911SC's.

Nick.

Any initial readings from the O2 sensor are ignored by the engine until a working temperature is reached. If this is happening upon startup, you may want to check other variables.