Volkswagen Golf/Jetta 2 manual

Catalytic converters - general information and precautions
Fuel and exhaust systems - K-Jetronic fuel injection - 8 valve engines / Catalytic converters - general information and precautions


The catalytic converter is a reliable and simple device which needs no maintenance in itself, but there are some facts of which an owner should be aware if the converter is to function properly for its full service life.

a) DO NOT use leaded petrol in a vehicle equipped with a catalytic converter - the lead will coat the precious metals, reducing their converting efficiency and will eventually destroy the converter.

b) Always keep the ignition and fuel systems well-maintained in accordance with the manufacturers schedule. Ensure that the air cleaner element, fuel filter and spark plugs are renewed at the correct intervals.

If the inlet air/fuel mixture is allowed to become too rich due to neglect, the unburned surplus will enter and burn in the catalytic converter, overheating the element and eventually destroying the converter.

c) If the engine develops a misfire, do not drive the vehicle at all (or at least as little as possible) until the fault is cured. The misfire will allow unburned fuel to enter the converter, which will result in its overheating.

d) DO NOT push or tow-start the vehicle.

This will soak the catalytic converter in unburned fuel, causing it to overheat when the engine does start.

e) DO NOT switch off the ignition at high engine speeds. If the ignition is switched off at anything above idle speed, unburned fuel will enter the (very hot) catalytic converter, with the possible risk of its igniting on the element and damaging the converter.

f) DO NOT use fuel or engine oil additives as these may contain substances harmful to the catalytic converter.

g) DO NOT continue to use the vehicle if the engine burns oil to the extent of leaving a visible trail of blue smoke. The unburned carbon deposits will clog the converter passages and reduce its efficiency. In severe cases, the element will overheat.

h) Remember that the catalytic converter operates at very high temperatures, hence the heat shields on the vehicles underbody. The casing will become hot enough to ignite combustible materials which brush against it. DO NOT, therefore, park the vehicle in dry undergrowth, over long grass or piles of dead leaves.

I) Remember that the catalytic converter is FRAGILE. Do not strike it with tools during servicing work, take great care when working on the exhaust system, ensure that the converter is well clear of any jacks or other lifting gear used to raise the vehicle and do not drive the vehicle over rough ground, road humps etc. in such a way as to `ground the exhaust system.

j) In some cases, particularly when the vehicle is new and/or is used for stop/start driving, a sulphurous smell (like that of rotten eggs) may be noticed from the exhaust. This is common to many catalytic converter-equipped vehicles and seems to be due to the small amount of sulphur found in some petrols reacting with hydrogen in the exhaust to produce hydrogen sulphide (H2S) gas. While this gas is toxic, it is not produced in sufficient amounts to be a problem. Once the vehicle has covered a few thousand miles the problem should disappear. In the meantime, a change of driving style or brand of petrol used may effect a solution.

k) The catalytic converter used on a wellmaintained and well-driven vehicle, should last for between 50 000 and 100 000 miles. From this point on, careful checks should be made at all specified service intervals of the CO level to ensure that the converter is still operating efficiently. If the converter is no longer effective, it must be renewed.


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