Rough Idle on cold start-up on Audi A4 1.8T B8.5

Problem Solved. So it was the thermostat that was faulty. Problem is that I did not address this problem on time, now with a faulty thermostat this causes the engine to run lean on a cold start, hence the rough idle. If this problem is not address on time (like mines) it causes misfires on all 4 cylinders hence stretching the timing chain. So now I also have to change the timing chain as well. If you ever have a problem like mines, please address it urgently otherwise it will end up costing you much more in the end.

thanks similar problem here... last week noticed my thermo housing was corroded and the mechanic fixed/changed it.... but now idling badly till warm... ? wonder if he did something wrong ? will get him to check it out again