I have a 2006 Honda Odyssey with 40K miles. The valves have been making a chattering noise for awhile now. I have tried different brands of gas (highest grade) - no luck. I took the car in to the dealer while it was still under warranty they could not find anything wrong. I took it again lately and they said not to worry. Well… I am a little worried. It seems like some sensor is not functioning properly but I could be wrong. Any ideas would be greatly appreciated.