I bought a 2007 prius with only 55000 miles after service it starts misfiring &shaking badly when the engine kicks on my mechanic could not solve the problem after trying every thing, what shall i do

buy something else, and don't go around thinkin' that a used hybrid is anything worth owning-

Thancks , this not an answer to my question, I already bought the car

There should be a simple answer: If there is a check engine light on the screen after the engine shake during start up, start there, the knock sensor code may be a trouble code. Also, if you have checked normal items like plugs and plug wires that is a good start. Does it run smoothly after the gas engine is running for awhile. Good news is the 2nd Gen prius is an amazing vehicle, I have owned several, a couple had 360,00 and 400,000 miles on original engine and batteries! It seems that they really just get broken in good around 150k.

If you decide to sell the prius, you can reach me at kmerida@yahoo.com