exhaust odor/idle MOT issue

[jondee86]

I don't have a catalytic converter and I have never smelled "pepper" from
an ehaust... but I do read a lot Apparently, if the gasoline in your country
contains sulfur, the combustion process will produce hydrogen sulphide in
the exhaust. The cat is supposed to convert this to sulfur dioxide which is
odorless. But if the cat is not working properly or if the engine is rich or has
a misfire, some of the hydrogen sulphide will not be converted and you get
the characteristic "rotten eggs" smell.

If your car does not get driven far or often, you may be getting a buildup of
carbon from low temperature operation. It might be a good idea to take the
car for a drive on a motorway where you can cruise at 100kph for half an
hour or more. This will help get the plugs, O2 sensor and cat up to their
correct operating temperature and "self clean" to some extent. See if that
makes any difference.

Changing the fuel filter is a good idea

Your car will have an "idle-up computer" that operates a small solenoid
valve to let extra air into the intake manifold. This will raise the idle speed
by around 100rpm when there is an electrical load such as brake lights,
head lights, rear screen heater etc.

Cheers... jondee86