Catalytic Converter: Testing and Inspection

CATALYTIC CONVERTER INSPECTION
- Visually inspect exterior of converter. If severe damage is noted, such as dented, crushed or rusted out shell, replace converter.
- Whenever converter is removed from vehicle, check ceramic element through exhaust inlet and outlet. If element is clogged, melted or otherwise damaged, replace converter.

FUNCTIONAL TEST
- Run the engine at 2,500 rpm for approximately 2 minutes to heat catalytic converter to operating temperature.
- Connect a surface temperature probe on exhaust inlet of catalytic converter and measure temperature.
- Connect surface temperature probe on exhaust outlet of catalytic converter and measure temperature.
- There should be at least 100°F (38°C) increase in temperature from the inlet to the outlet.
- If temperature differential is less than specified, catalytic converter should be replaced.

EXHAUST RESTRICTION CHECKS:

MANIFOLD VACUUM TEST
- Connect vacuum gauge to manifold vacuum source.
- Start engine and idle. Note vacuum reading, and record.
- Run engine at approx. 2,000 rpm with no load.
- Note vacuum at steady engine speed. If vacuum is less than previous (idle) reading by greater than 75 mmHg (3 in.Hg), a restricted exhaust system is indicated.

Exhaust System Back Pressure Check (Using Oxygen Sensor Mounting Hole):

EXHAUST PRESSURE METHOD AT OXYGEN SENSOR OR CO TEST PIPE
- Install exhaust backpressure tester in place of Oxygen sensor (or CO test pipe).
- With engine idling at normal operating temperature, the gauge reading should not exceed 8.6 kPa (1.25 psi).
- Increase engine speed to 2000 rpm. Gauge reading should not exceed 20.7 kPa (3 psi).
- If backpressure at either speed exceeds specification, a restricted exhaust system is indicated.
- Inspect exhaust system for a collapsed pipe, heat distress or possible internal muffler failure.
- If no obvious reasons for excessive exhaust system backpressure are found, suspect a restricted catalytic converter.
- After completing test, coat threads of oxygen sensor (if removed) with anti-seize compound prior to reinstallation.