Catalytic Converter: Testing and Inspection
***UPDATED BY TSB #F03092, OCTOBER 19, 1992FAULTY CONVERTER SYMPTOMS
^ Lack of power
^ Idle speed drops
^ Engine stalls
^ Rattle in the exhaust
CONVERTER DAMAGING CONDITIONS
^ Engine misfiring (bad spark plugs, ignition wires, connections, etc.)
^ Ignition timing out of adjustment
^ Extreme loads on engine (pulling a trailer, mountain driving, etc.)
^ High speed driving at high outside temperatures.
^ Using leaded or high sulfur fuel.
VISUAL INSPECTION
1. Visually inspect exterior of converter. If severe damage is noted, such as dented, crushed or rusted out shell, replace converter.
2. 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
1. Run engine at 2500 rpm for approximately 2 minutes to heat catalytic converter to operating temperature.
2. Connect a surface temperature probe on converter inlet and measure temperature.
3. Connect temperature probe on converter outlet and measure temperature.
^ Outlet should be at least 100°F (38°C) hotter than inlet.
4. If temperature differential is less than specified, converter should be replaced.
EXHAUST RESTRICTION CHECKS:
Manifold Vacuum Test
1. Connect vacuum gauge to manifold vacuum source.
2. Start engine and idle. Note and record vacuum reading.
3. Run engine at approximately 2000 rpm with no load. Note vacuum at steady engine speed. If vacuum is less than previous (idle) reading by greater than 75mm Hg (3" Hg), a restricted exhaust system is indicated.
Exhaust Pressure Method At Oxygen Sensor Or CO Test Pipe
Exhaust System Back Pressure Check (Using Oxygen Sensor Mounting Hole):
1. Install exhaust backpressure tester in place of Oxygen sensor (or CO test pipe).
. With engine idling at operating temperature, gauge reading should not exceed 8.6 kPa (1.25 psi).
3. Increase engine speed to 2000 rpm. Gauge reading should not exceed 20.7 kPa (3 psi).
4. If backpressure at either speed exceeds specification, a restricted exhaust system is indicated.
5. Inspect exhaust system for a collapsed pipe, heat distress or possible internal muffler failure.
6. If no obvious reasons for excessive exhaust system backpressure are found, suspect a restricted catalytic converter.
7. After completing test, coat threads of oxygen sensor (if removed) with anti-seize compound prior to reinstallation.
Drop Test
1. Remove converter. Hold vertically and drop from about 20 cm (8 in) on to a block of wood.
2. Turn converter over and drop it on its other flange from the same distance.
3. If a slight knocking sound is heard from inside converter, or if ceramic grid moves inside the housing, converter is damaged and should be replaced.