Well first I heard a rattle coming from under the car and didn't know what the hell it was. About 2 weeks later my car starts doing this when cold: cranks, wont start, cranks starts shuts off, cranks and drives fine and it does this everytime it is cold or has been sitting for an hour or so. Well turns out the rattle is coming from my catalytic converter. I can't afford to get it replaced for a week or so. Do you guys think this has anything to do with the starting problem?

97 a4 2.8 2wd

 

the cat probably doesnt have anything to do with your starting problem as it is not constant. does it start easier if you turn the key to the on position for 10 seconds before you crank it? if yes- look at the fuel pump. if no- look at either the coolant temp sensor or intake air temp sensor.

 

A bad coolant temp sensor can cause weird starting problems, mine did. And the rattle is more likely to be your wastegate acuator rather than your cat. you can tighten the wastegate actuator arm to help with the rattle.

 

its a 2.8^^ no wg

 

No it's def the cat, i had my ear up to it and when it was off i hit the cat with my hand and it rattles badly.

Do you think that this could have something to do with the serpentine belt? I had it off when I replaced the ps pump. It could be loose??