my 2.8qm has been spewing warm air even with the a/c on, and lately, i have noticed a slight rattling noise when i turn it on. i know that my driver's side cat is bad, and figured that the rattling could be from that and that i just need to recharge my a/c, but the rattling gets when i turn on the a/c and lessens when i turn it off. do i just need to recharge it and swap out the catalytic converter, or is there something else that will need fixed?