oxygen sensor wire purpose?????

[turbopower]

I noticed today that oxygen sensor wire has fallen off on my Cordia turbo, can it make any difference to way my car is running or is it there just for measuring purposes??????
I run Microtech microfueller and im just thinking that oxygen sensor might tell to the computer how much fuel to give, or is it over vacuume?...and i noticed that cars runs rich lately, and also ignition pulse light on Microtech doesnt come off even though the car is turned off, before it would go off after a while but now it stays on...maybe im imagining things hehe...

[smeck]

Without the reading from the O2 sensor, the ecu can't calculate the set the mixture accurately. When the systen is running in properly, the O2 reading is used to lean/richen the mixture to give better efficiency and economy. Without it, the ecu has to use fuel maps to pick the mixture, so your car will run rich. This will also eventually foul the spark plugs and places excessive load on the ignition system.

[turbopower]

I did a bit of research and now i have some idea of oxygen sensors purpose, anyway i found out today that the wire to o2 sensor is disconnected, maybe it was bad connection there before, or maybe sensor is damaged, but my car spends heaps of fuel lately, and condition of plugs shows that as well, the car does not smoke, compression is even on all cylinders but few times i had car detonating and coughing large amounts of black smoke prolly unburnt fuel...
For a record car is Mitsubishi Cordia turbo, bit modified has extra injector controlled by Microtech microfueller, 3 inches exhaust, hybrid turbo running 15 psi, supra cooler etc.
Anyway the ignition pulse light on Microtech microfueller doesnt turn off now the sensor is disconnected, does it have anything to do with it as before it would turn off after a while...
The car spends close to 20l/100km??????

[smeck]

Without the O2 sensor, your ecu is like a cat without whiskers. Repair the connection or replace the sensor, you'll save the cost in fuel.