GM Full Size Vans 1987-1997 Repair Guide

Catalytic Converter



The catalytic converter is a muffler-like container built into the exhaust system to aid in the reduction of exhaust emissions. The catalyst element is coated with a noble metal such as platinum, palladium, rhodium or a combination of them. When the exhaust gases come into contact with the catalyst, a chemical reaction occurs which reduces the pollutants into harmless substances such as water and carbon dioxide.

Two types of catalytic converters are used on Chevrolet/GMC full-size vans: an oxidizing type and a three-way type. The oxidizing catalyst requires the addition of oxygen to spur the catalyst into reducing the engine's HC and CO emissions into H 2 O and CO 2 .


  1. Use only unleaded fuel.
  3. Avoid prolonged idling; the engine should run no longer than 20 minutes at curb idle and no longer than 10 minutes at fast idle.
  5. Do not disconnect any of the spark plug leads while the engine is running. If any engine testing procedure requires disconnecting or bypassing a control component, perform the procedure as quickly as possible. A misfiring engine can overheat the catalyst and damage the oxygen sensor.
  7. Make engine compression checks as quickly as possible.
  9. Whenever under the vehicle or around the catalytic converter, remember that it has a very high outside or skin temperature. During operation, the catalyst must reach very high temperatures to work efficiently. Be very wary of burns, even after the engine has been shut off for awhile. Additionally, because of the heat, never park the vehicle on or over flammable materials, particularly dry grass or leaves. Inspect the heat shields frequently and correct any bends or damage.
  11. In the unlikely event that the catalyst must be replaced, DO NOT dispose of the old one where anything containing grease, gas or oil can come in contact with it. The catalytic action with these substances will result in heat which may start a fire.