I recently filled up my oil as it was getting a bit low and then drove it up the street and after about 500m a massive cloud of smoke was pouring out from the back of the car. i let it cool down for about 15min and when i started it up again it was missing and idling rough and couldn't maintain a constant rpm. i think i may have over filled the oil but would that cause smoke out of the exhaust and the poor engine performance. also when i turned the car on the temp gauge wasn't working and this is the first time i have noticed that. any ideas as what the problem could be??

Have you checked the amount of oil added??

What colour is the smoke? I once accidentally over-filled the oil in my other car (significantly, because I had a faulty oil pressure switch that had me confused), and the car was billowing huge amounts of white smoke out the exhaust.

if you overfill by a fair bit the oil will come out the exhaust in thick white smoke.
it will foul your plugs and car will idle like ****.
drain the oil out so its at the right level
then take the spark plugs out and wash/spray them in wd40 to clean them and get rid of the oil
then fit them back and start car
this should work if the problem is overfilling of oil
 
as for you temp. gauge not working im not sure what the issue is but first checka nd see if the temp. sensor connection (its near the coolant neck next to the block on the turbo, im not sure where the n/a one is located) is unplugged.
 
might also want to check and see if you have enough coolant etc
 
cheers

Its blowing out white smoke not a blue like colour, hopefully it is just an overfill of oil because when i was driving it it seemed fine until all of a sudden... 
 
Thanks for the quick reply guys

"when i turned the car on the temp gauge wasn't working"
After start up, with a 3SGE the temp gauge should start to move up after 2 - 3 minutes or so from dead cold.
How long was it running before you saw the gauge wasn't moving?
 
 
 

i drained the oil and ran it for a while and eventually the smoke has stopped and cleaned out the spark plugs and now all fine. as for the temp gauge when its back working fine now but when i noticed it wasnt working i was driving for about 3-4mins and it didnt move.  
 

Great, so it looks like the motor is OK.
 
I have noticed on my car it takes noticeably longer for the temp gauge pointer to move in very cold weather.

Reddtarga

Great, so it looks like the motor is OK.

I have noticed on my car it takes noticeably longer for the temp gauge pointer to move in very cold weather.

longer than usual or longer than other cars??
SW20's and AW11's take ages to heat up compared to a normail car cause iron blocks take longer than alloy, and once the block heats up theres an aweful lot of cold water sitting in the cooling system... a LOT more than an average car cause of the distance to the radiator.  On mine i can see the needle drop back down when the thermostat opens... like its a two stage warming process....

^mine does that when I slide the temp to HEAT, drops the temp needle for a bit.
that because most 'other' cars don't have 14L of coolant to contend with.