New catalytic converters may smell of rotten eggs when first installed; this is normal
and should dissipate after some hours or days of driving.
Sulfur dioxide emissions come from hydrogen sulfide gas which, when converted by
a functioning catalytic converter, should dissipate into innocuous sulfur dioxide gas.
If the smell lingers it could indicate that your converter has stopped working correctly.
Sulfur Smell
An exhaust smelling of rotten eggs could be caused by any number of factors; one
such source should be your catalytic converter. Catalytic converters work to reduce
emissions and pollution by converting hydrogen sulfide and other harmful chemicals
to sulfur dioxide – this requires them to get very hot; any malfunction will emit an
unpleasant odor into your car’s exhaust system.
Your engine’s exhaust could be emitting the scent of rotten eggs due to an issue
with either its battery or fuel pressure sensor. A malfunctioning fuel pressure sensor
could allow too much fuel into your combustion chamber, creating a sulfur smell in
its wake.
If the smell is coming from inside the cabin, it could be due to an exhaust system
leak behind the catalytic converter. New exhaust components (including converters)
come equipped with an oil coating designed to protect them from rusting when
shipped directly from their manufacturer to their shop – however this will
subsequently wear off once heated by heat from driving and the part heats up
properly for its first time in use.
Gasoline Smell
The catalytic converter reduces emissions by transforming sulphur gases like
hydrogen sulfide into innocuous sulfur dioxide during combustion – an operation
performed in both gasoline and diesel engines. If your exhaust smells of gasoline, it
may indicate that your catalytic converter hasn’t been working effectively; this could
also cause your engine to run rich, leading to poor acceleration and fuel economy.
New catalytic converters typically come with an oil coating to protect them during
storage and should wear off within several miles of driving. If rotten egg or gasoline
odors still pervade after having replaced a converter, there may be another
mechanical issue causing this. Engine misfire, burning oil leakage or an air filter clog
could all be causes – if these issues remain unfixed the catalytic converter could
soon fail again.
New Converter Smell
Catalytic converters help reduce harmful emissions by transforming engine exhaust
into less harmful gasses, via chemical reactions. A newly installed converter may
smell for several days after initial activation.
This unpleasant aroma stems from hydrogen sulfide in fuel being converted to sulfur
dioxide by the catalytic converter and released through your tailpipe as exhaust
gasses. If this odor does not dissipate quickly after installing a new catalytic
converter, it could indicate something is amiss with your vehicle.
If your mechanic installed a new catalytic converter and you detect an unpleasant
odor lingering from it, have them inspect it immediately. It could be that something
else is causing this rotten egg smell; inspection should reveal any issues with o2
sensors or exhaust piping that need attention; low engine oil levels might also be the
source.
Old Converter Smell
An exhaust pipe that emits an unpleasant rotten egg smell could be an indicator
that your catalytic converter is malfunctioning, as its function should be to convert
hydrogen sulfide to sulfur dioxide in an odorless way and eliminate hydrogen sulfide
emissions. Sulfate-laden gasoline binds with oxygen as it exits your engine and
contributes to this smelly emission.
An improperly working converter can make your vehicle run poorly and produce
more pollution, decreasing fuel efficiency. Furthermore, this may trigger an engine
light or warning message as well as darken the smoke leaving its tailpipe.
Before new catalytic converters can begin their task, they need to be broken in. A
shop replacing them should follow a procedure which includes starting and idling
until normal operating temperature has been achieved, before revving up to full
speed for two minutes at high revs until it heats up completely for the first time. This
enables it to heat up properly for use.