General description
To reduce the emission of unburned hydrocarbons (NS), carbon monoxide (SO) and nitrogen oxides (NOx) late model vehicles described in this manual are equipped with a catalytic converter. The converter contains a ceramic honeycomb accumulator plated with noble metals that accelerate the reaction between the pollutants mentioned above and the oxygen in the exhaust gases. Pollutants are oxidized to form water (H2O), nitrogen and dioxide (CO2).
Typical catalytic converter (shown for M10 engine, others are similar).
Examination
1. Visually inspect the transmitter (converters) for cracks or damage. Make sure all gulls and turns are tight.
2. Check the insulating cover (if installed), welded to the transducer - it must be firmly fixed.
If the insulating cover is dented so that it touches the transmitter housing, overheating of the floor may occur.
3. Start the engine and leave it idling.
4. Check for exhaust gas leaks across the converter flanges. Check the presence of openings in the housings of all converters.
Component Replacement
1. Raise the vehicle and place it on jack stands.
2. Inspect the catalytic converter for cracks or damage.
3. Check the transducer connections for tightness.
4. Check the insulating jacket welded on top of the catalytic converter to protect against damage and reduce mounting stress.
If the insulating jacket is dented so that it touches the inner case of the inverter, excess heat may be transferred to the floor.
5. Start the engine and let it idle. Check all exhaust system connections for exhaust gas leaks.
Precautions
The catalytic converter is a reliable and simple device that itself does not require maintenance, but there are some circumstances that must be considered if the correct operation of the converter during its entire service life is of interest.
- Do not use leaded gasoline on a vehicle with a catalytic converter - lead will deposit on the precious metals, reducing efficiency and destroying the converter.
- Always maintain the ignition system and fuel system in accordance with the manufacturer's requirements, as indicated in Chapter Car maintenance. In particular, do not forget to replace the air cleaner filter element, fuel filter (if installed) and spark plugs. If the air/fuel mixture is too rich, unburned fuel will enter the catalytic converter, overheating the element and destroying the converter.
- If the engine skips flashes, do not drive the car at all (or as little as possible), until the problem is corrected - skipping the flash causes unburned fuel to enter the converter, resulting in the overheating described above.
- Do not start the vehicle by towing or "with a push" - this will introduce unburned fuel into the catalytic converter, which will cause overheating after starting the engine - see (b) And (With).
- Do not turn off the ignition at high engine speeds, that is, do not press the throttle pedal before stopping the engine. If the ignition is turned off while not idling, unburned fuel will enter the (very hot) catalytic converter with the possibility of ignition and damage to the converter.
- Do not use fuel or engine oil additives - they may contain substances harmful to the catalytic converter.
- Do not operate the vehicle if a noticeable amount of blue smoke comes out due to hot engine oil - unburned carbon deposits will clog the converter channels and reduce its efficiency; in some cases the element will overheat.
- Remember that the catalytic converter operates at very high temperatures, hence the heat is reflected off the floor of the vehicle - the shroud becomes hot enough to ignite materials stuck to it. Therefore, do not stop the car on dry grass, on piles of dry leaves and in tall grass.
- Remember that the catalytic converter is fragile - do not hit it with tools while working on the exhaust system. Make sure the inverter is far enough away from jacks or other lifting equipment, and do not drive the vehicle on rough roads, bumps, or other places where the inverter could be caught on the ground.
- In some cases, in particular when the vehicle is new and/or used in start/stop mode, the smell of sulfur may appear in the exhaust gases (smells like rotten eggs). This often happens with vehicles equipped with catalytic converters and is due to the small amount of sulfur in some gasolines, which reacts with the hydrogen in the exhaust gases to form hydrogen sulfide (H2S); - although this gas is toxic, it is not produced in such significant quantities as to be a problem. After the car has driven the first few thousand kilometers, the phenomenon should disappear - otherwise, change the driving style or brand of gasoline, this may solve the problem.
- The catalytic converter on a well maintained and properly operated vehicle will last between 90,000 and 180,000 kilometers - after which the CO level should be regularly checked carefully to monitor the efficiency of the converter. If the converter has lost efficiency, it should be replaced.