i have no idea.. i just bought this car three weeks ago i dont even know if the valves have ever been adjusted. But if it was the valves wouldnt the check engine light come on or would the computer not read that? and yes that is really the only symptoms is a rattling sound almost as if a pipe is rattling. i hear it by my drivers door but you know how sound carries so i couldnt tell you where it is truely coming from.