Fuel System - Sulfur (Rotten Egg) Exhaust Smell
309-01DATE
5/98
V8 XJ Series/XK8
MODEL
1997 MY-ON XK8 Range
1998 MY-ON V8 XJ Series
VIN
001001-ON
812256-ON
Sulfur (Rotten Egg) Odor - Fuel Quality - Reference Information Only
Issue:
Customers may have concerns over sulfur odors ("rotten egg" smells) emitted from the exhaust system of modern vehicles equipped with three-way catalytic converters.
Typical situations may be during hard acceleration, when idling after suddenly slowing from cruising speeds, or when leaving the vehicle immediately after switching the engine off. Customers operating convertible vehicles with the convertible top raised may notice such smells more than users of closed sedan and coupe vehicles.
BACKGROUND:
The source of these odors is the sulfur that is present in all gasolines.
The amount of sulfur compounds in the fuel may vary considerably, depending on the sulfur content of the crude oil from which the fuel was derived and the processes utilized in a particular oil refinery to control the sulfur content of the final product. As a result, the sulfur content of fuel may vary from brand to brand, while in certain larger countries a particular brand of fuel may be sourced from more than one oil refinery, and may thus vary in sulfur content from one region of the country to another.
During normal vehicle operation under relatively lean mixture conditions (typically steady cruising) the majority of the sulfur in the fuel is converted by the combustion processes and the catalytic converter into Sulfur Trioxide, a gas which passes into the atmosphere with no perceptible odor.
However, a characteristic of all three-way catalytic converters installed in the exhaust systems of modern vehicles is for the converter to "store" a portion of sulfur compounds on the active surfaces of the catalyst units when the engine is operating under cruising conditions. Under relatively rich mixture conditions (typically idling or hard acceleration) this residual sulfur is then converted into hydrogen sulfide - a gas having the characteristic and very noticeable "rotten egg" odor.
This characteristic is common to vehicles of all manufacture - not just Jaguar - all of which share the same technology in their catalytic converters, on a worldwide basis.
ADVICE TO CUSTOMERS:
When cruising on multi-lane highways with other vehicles in close proximity, the source of any hydrogen sulfide odor is likely to be from adjacent vehicles. Adjustment of air conditioning controls to reduce, or even shut off (recirculation mode), the fresh air taken in at the front of the vehicle may sometimes result in an improvement during temporary conditions.
When the source is the customer's own vehicle - typically a complaint of odors noticeable immediately after garaging the vehicle with the engine hot - there are certain recommendations to be made:
^ Experiment with different brands of fuel. Different brands may contain less sulfur. It may take several tanks of fuel before any improvement is noticed.
^ Ensure that the owner is using premium fuel. Premium quality fuel is likely to contain less sulfur than "regular" quality fuel. Again, it may take several tanks of fuel before any change is noticed.
^ Unusual driving or climatic conditions may have an effect on odors noticed by the occupants. For example, in very slow-moving heavy traffic a tail wind may blow the vehicle's own exhaust gases forward where they are pulled into the interior of the vehicle by the climate control system fan, or may be noticed immediately by the occupants of an open-top convertible vehicle.
Action:
Dealers should be aware that it is also a characteristic of three-way catalytic converters that as mileage increases, there is a tendency for hydrogen sulfide odors to become less noticeable - typically, this effect may be noticed after 6,000 - 10,000 miles from new (10,000 - 16,000 km;). If a three-way catalytic converter is replaced, odors are more likely to be noticed than on a vehicle with its original converter.
NOTE:
REPLACING A CATALYTIC CONVERTER SET WILL NOT SOLVE COMPLAINTS OF SULFUR ODOR.
Warranty Information:
This Technical Bulletin is to provide advice only, and is not a recommendation to perform repairs of any description.