Hello got a question...
my car starts up on the first shot then it will go up to 3500 rpm, and the down to around 1200 rpm for awhile then it will make this don don sound... then after a min or so ...it will drop to 750 -800 .
just dont know what that is .... can anyone help me out ?

New spark plugs on the way here (dont know if that will fix the don don sound .

Thanks