Just got the car back from the garage after developing a water leak. Asked them to also check for a rattle underneath the car. Turn's out there is something that has come loose inside the catalytic converter. Anyone else heard of this and i suppose a new cat is required? Thank's in advance and Merry Chrimbo.

Hi, 

Yes I had the same and fault code PO420 on the o/s cat.

As I run on lpg I don't the cats to pass a mot I removed them and gutted them. I then fitted  a 90 degree 02 extender to both down stream 02 sensors, these 'pull' the sensors out of exhaust gases so they can't see/read that theres no cats (and cause fault codes).

It was worth doing as it revs more freely, sounds louder and pulls better.

I did also find out that facelift cats are different to pre facelift and they can't be swapped!

Sorry I know this does help you.

This is what is came out of one cat -

Hi

cats usually fail when they have run lean, they get too hot and melt, usual culprit is a failing lambda sensor can cause a one bank to run lean

LPG has the same effect as well, lpg cars can run hotter and cause higher exhaust temps, melting cats and other common problems are valves on lpg cars

industrial gas and lpg engines usually have special valves to combat this

cheers

Joe

Just for the record, my rattly cat and fault code were present then I got the car and I fitted the lpg.