I am not sure which sensor this is, on the drivers side of the engine, looks like exhaust sensor? Its not plugged in :\ What might arise from this? I dont think it was ever plugged in, and when i do plug it in, the car seems to run funny, slight shudders and such i suppose.

 

I think it's the 2nd O2 sensor (exhaust).

 

How nessecary is it, and what happens with/with out it?

 

It's probably your Oxygen Sensor . It monitors the air/fuel mixture , so if it's not hooked up you might as well buy a new one for about 20 bucks from your local parts store and hook it up .