sometimes ( mostly in the morning) when i start the car I can hear few knocks, they come up with diferent time intervals ( not even knock knock..) it has a second or two between knocks, knocks from 2 to 4 or 5 times and then disapears.. what the hell? can it be the VVT solenoid? I can hear it from inside ( it's pretty loud) and it sounds like someone is actualy knocking on the bonnet from under it .... I use a semi synthetic oil ( if it makes any diference) so I would be thankfull for any help...