90CS Quattro V6-2.8L (AFC) (1995)
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Catalytic Converter: Testing and Inspection
SYMPTOMS OF A FAULTY CATALYTIC CONVERTER ARE:
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Poor power output.
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Idle speed drops.
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Engine stalls.
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Rattle in the exhaust.
THE CONVERTER CAN BE DAMAGED BY:
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Engine misfiring (bad spark plugs, ignition wires, connections, etc.).
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Ignition timing out of adjustment.
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Straining engine (pulling a trailer, mountain driving, etc.).
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High speed driving at high outside temperatures.
THE CATALYTIC CONVERTER CAN BE CHECKED IN SEVERAL WAYS
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 the engine at 2,500 rpm for approximately 2 minutes to heat catalytic converter to operating temperature.
2.
Connect a surface temperature probe on exhaust inlet of catalytic converter and measure temperature.
3.
Connect surface temperature probe on exhaust outlet of catalytic converter and measure temperature.
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Outlet should be at least 100°F (38° C) hotter than inlet.
4.
If temperature differential is less than specified, catalytic converter should be replaced.
EXHAUST RESTRICTION CHECKS:
MANIFOLD VACUUM TEST
1.
Connect vacuum gauge to manifold vacuum source.
2.
Start engine and idle. Note vacuum reading, and record.
3.
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
75mm Hg (3" Hg), a restricted exhaust system is indicated.
DROP TEST
1.
Remove converter from the car.
a. Hold the converter vertically and drop it from about 20 cm (8 in) on to a block of wood.
b. Turn the converter over and drop it on its other flange from the same distance.
c. If a slight knocking sound is heard from inside the converter, or if the ceramic grid moves inside the housing, the converter is damaged and
should be replaced.
