I have a 2003 Nissan Maxima an I having so much problem. I have a rattling noise coming from the catalytic converter. An now the check engine light is flashing an the car is jerking an wants to shut off. Does anyone knows what is going on. Did anyone else have any similar problems......

 

If you have access to a scan tool you need to get the codes to help diagnose your problem. Get the codes then check back. It could be any number of things like a bad misfire do to a bad coil or coils, MAF, TPS a bad 02 sensor. It's pretty tough to diagnose until you get the codes and the rattling noise coming from your catalytic is probably just the heatsheild.

 

Had a similar issue, i had bad spark plugs and coils. Replaced them and haven't had that issue since. Hope that helps.

 

Sounds like you're misfiring and may have a bad cat as mentioned before get those codes ASAP