One problem related to loud engine noise has been reported for the 2005 Honda Civic Hybrid. The most recently reported issues are listed below.
It lurches for it will excell when you don't want it to. Has trouble to shift into another gear loud noises. Was driving down the highway and I turned on the cruise control an accelerated faster than when I program data entry of the rpm's up. Had to step on the brakes a couple times to get it to stop doing that almost hit two vehicles I do all the transmission fluid changes recommended and oil. These are great cars but these problems that need to be addressed.