Hi everyone, My first post but used your search engine to learn alot about our Prius (2010 about 20000km).Thankyou. We have been having trouble with "rough engine cold start" problem as mentioned in some of your posts and seen on youtube, and have used some of the suggestions as supplied. Long story short, it became worse and we were able to reproduce at the local dealer.It ended up being No4 fuel injector although on Toyota Australia orders all 4 injectors were replaced under warranty (and on pulling them out all were partially blocked). Have been told to put a additive (supplied by dealer) in fuel tank every 2 or 3 fills and for me to take it driving sometimes and give the Prius a bootfull (my wife drives it and mainly around town). Anyway I hope this helps anyone having this problem and again thanks for providing a very helpful forum. regards Trev.