I was wondering how much difference it will make when tuning a car, if, the o2 sensor is out causing it to be running with a CEL 1 as i tuned my maps that way and hve recently read that it will affect it when i put the o2 sensor back in to get rid of the CEL

 

It'll be fine... basically what you're doing is throwing the ECU into a forced open loop.

 

I kept my o2 plugged in, but it is just hanging in the engine bay now because I haven't got an o2 bung in the downpipe yet. Surprisingly no CEL, so this is just making me run rich, right? So, if I were to just disconnect the sensor, it would just be in open loop, not limp mode?

 

how do you tune closed loop then or is this not possible in TE? then again i'm not really that bothered as closed loop is only for fuel economy isnt it

 

Tune the part throttle portion of your maps correctly, and the ECU will calculate from those and O2 and a few other sensors to get good fuel management during closed loop.