Firstly, catalytic converters very seldomly need replacing. Replacing
a cat is very expensive and to find you haven't cured the problem
would be annoying wouldn't it. Let's look at what the smell actually
is, why it is occuring and how best to address the problem.
The sulphur smell (rotten eggs) from the exhaust, is actually caused
by running the engine (and therefore also the catalytic convertor)
slightly lean for long periods and then running under a rich condition
(I.E. going up a hill under heavy load). This is when the sulphur
smell (rotten eggs) is produced.
Under relatively lean conditions, the sulphur found in petrol is
converted to sulphur trioxide, then during the rich running condition
the sulfur trioxide is converted into hydrogen sulphide (rotten eggs
smell) within the catalytic converter.
The petrol / sulphur content of your brand of fuel and the
characteristic of catalytic convertor to store sulphur compounds and
release them during rich engine running conditions is the main cause
of this problem. Switching petrol brands may help. The oxygen sensor
may also need to be replaced to correct a fuel injection mixture
Get yourself along to a garage that has a gas analyser and see exactly
where your mixture is. Make sure this is right, and THEN start to
look elsewhere. A gas check should only set you back a few pounds. If
you're in the UK take the car to an MOT station, they have the
equipment to check this problem out for you. Hydrogen sulphide stinks,
I understand why you want this sorted out :)
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