The catalytic converter is located in the exhaust system prior to the muffler. The catalytic converter is an emission control device added to the gasoline exhaust system to reduce hydrocarbon and carbon monoxide pollutants from the exhaust gas stream.
There are 3 types of catalytic converters: Conventional Oxidation Converters (COC), 3-Way Catalyst (TWC) and dual bed catalytic converters which are a combination of both the above mentioned. All catalytic converters are of 2 designs: a honeycomb-type block which is non-serviceable, or a small canister containing catalytic beads.
Both converters contain a base material of alumina impregnated with platinum/palladium, while 3-way catalysts in addition to this also contain a material coated with platinum/rhodium. Both converters reduce hydrocarbons and carbon monoxide, while the TWC also reduces oxides of nitrogen.
Note. Use only unleaded fuel on vehicles equipped with a catalytic converter. If leaded fuel is used, coating and destruction of the catalytic surfaces will result and replacement is required.
On some models, a TWC is used in conjunction with a COC both contained in the same canister. Working in conjunction with this, there often is an air injection pipe. This pipe injects air between these 2 beds to help further oxidize the exhaust gases. This is called a dual-bed converter.
HEAT SHIELDS
The combustion reaction, which is furthered by the converter, releases additional heat into the exhaust system. Temperatures in catalytic converters can reach 1600°F (870°C) under normal conditions. Special heat shields are therefore used to protect the underbody and under-vehicle components from this extreme heat.
MAINTENANCE
There is no scheduled maintenance of a catalytic converter, it is designed to last the lifetime of the vehicle. If it does not perform correctly, replace it. On some vehicles equipped with bead type converters, the lower outer shell can be replaced.
Scheme 48
- Remove the bottom cover by making a shallow cut close to the bottom outside edge. (Scheme 48) A shallow cut is required to avoid damage to inner shell. DO NOT remove fill plug.
- Remove insulation and check inner shell for damage. If damage to inner shell is found, entire catalytic converter must be replaced.
- If no damage is found, position new insulation into replacement cover. Apply a heat resistant sealer around edge of cover, using extra sealer at front and rear of pipe openings.
- Install replacement cover on converter and position retaining channel along edges. Complete installation by attaching clamps, provided with replacement cover, to both ends of converter and tighten.
RESTRICTED EXHAUST SYSTEM
A restricted or blocked exhaust system usually results in loss or lack of power or popping through carburetor. Ensure that the condition is not caused by timing or ignition problems before testing for restricted exhaust system.
See appropriate flow chart in COMPUTER COMMAND CONTROL article.