Catalytic Converter: Testing and Inspection

Three-Way Catalytic Converter (TWC):

If excessive exhaust system back-pressure is suspected, follow this procedure to test the Catalytic Converter:
1. Attach a vacuum gauge to a manifold vacuum source and record a base pressure value with the engine idling.

2. Test drive the vehicle and monitor the vacuum gauge.

^ On moderate acceleration, the vacuum gauge reading should, at first, drop (toward 0 mm-Hg) and then rise to approximately the idle pressure value.

^ A pressure reading that does not return to near idle pressure value or continues to drop may indicate a restriction in the exhaust system.

3. If excessive exhaust system back-pressure is confirmed, remove the TWC from the car and make a visual check for plugging, melting or cracking of the catalyst.

4. Replace the TWC if any of the visible area is damaged or plugged.