Just happened last night sounds Like Rattling noise coming from under my car very loud "1990 240sx" and also sounds like my engine has a ticking noise sounds kinda of like a lawnmower . I plan on selling my 240 :/ but before I do I need to fix this thing
Did A little Research
People say it can be a heat shield .. and I can tighten it . But the only thing is I dont know how or where the heat shield is even located or how it looks

and people say It can be a clog in my cat . I know where thats at just dont know If I can fix that my self and if so how

Thats pretty much it thanks