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


Asked by Jul 27, 2019 at 01:45 AM about the 2013 Audi A4

Question type: Maintenance & Repair

Hello, I have a 2013 Audi A4 1.8T B 8.5 (petrol). During a cold start-up the
engine rough idles and sometimes shuts off. I have to rev it up a little until its
warm. Once it warms the problem goes away. I changed spark plugs, PCV
valve, HPFP but still have this problem. Any help will be greatly appreciated.

2 Answers


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.

1 people found this helpful.

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

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