Thats a little vague, but since the honda accord for 2008 in a 4 cyl has a timing chain, and a v6 has a timing belt it depends on which size engine you have. if it is the model with a timing chain i would suggest looking at that, and your serpentine belt, both of those can cause issues. Also, this may sound stupid, but look for objects that were left in the engine... i had a mechanic leave a wrench after he replaced my water pump in one of my cars