Xantia catalytic converter

[froggy]

Hi, my S2 Xantia, when idling the cat sounds like it is rattling around in the exhaust ! under revs ,,,, nothing. my question is do I replace the whole section or just the cat ? cheers Terry.

[quintet]

I would replace just the catalyst, if you can get under the car and give the catalyst a few firm thumps you can usually tell if the catalyst has broken up as it's give a fairly noticeable rattle, do not try this until the catalyst has gone cold, they operate at very high temperature.

[davoxx]

Could be a loose heat shield

[froggy]

Replaced the broken catalytic converter. it was broken and badly sooted up. The car , when cold, has a flat spot in second gear, for a few seconds. Then it picks up and out pours loads of black smoke. When the engine is warm, it runs lovely. is it the fault of the broken cat? if so, will it clear itself of this lumpy, smokey running? cheers Terry.