I am facing the above problem. Google Search is my default search engine where as at times, goes redirected to Yahoo engine:
http://us.yhs4.search.yahoo.com/yhs/search?hspart=newnet&hsimp=yhs-looksafe_ds_trans&type=266735_1655_usa_0_0_0_1_&p=technology%20details4
I have done the basic attempts to remove but in vain. Relevant details are: Using Lenovo make Z-580 model laptop with Windows 8 platform, Google Chrome + as browser and AVG 2014 Anti-virus and Malwarebytes for antivirus and antimalware solutions.
Please advise me suitable steps how to go about removal of this problem for which I shall be thankful to you.