I have not been able to track this down but I will try to explain what the noise sounds like. In cold weather when I start up my KIA and for the first few minutes it has a ratteling sound from the engine compartment. It does not sound good and I definately drive slow till the noise stops. The noise incresase when accelerating but subsides in normal driving when cold. I was thinking cheap gas might be the cause but I use Shell 87 octane. I also keep my injectors clean with Shaeffers supliment which works very well in all y other cars. I am religeous about oil changes and only run Amsoil as I have for the past 25 years in all my cars. Got any ideas on this one? Thank you