Initial Inspection and Diagnostic Overview

VISUAL INSPECTION
Inspect Catalytic converter for external cracks. Repair or replace as necessary.

BACK PRESSURE
If excessive exhaust back pressure is suspected, eliminate the exhaust system as a cause. If exhaust back pressure remains excessive with all mufflers disconnected, the catalytic converter may be plugged.

LOOSE CORE
If the exhaust system rattles during engine operation, check the catalytic converter for a loose core. With the vehicle raised (for access), tap the catalytic converter with a rubber mallet. If the converter rattles, the core is loose and the converter must be replaced.

FUNCTION CHECK
If all other emission systems are functioning correctly, but vehicle still has excessive tailpipe emissions, the catalytic converter core may by contaminated. To check converter effectiveness, perform the following check:

1. Warm the engine to normal operating temperature.
2. Run the engine at 2,500 RPM for 30 seconds.
3. Using a pyrometer, measure the exhaust pipe temperature before and after the catalytic converter.
4. Exhaust pipe temperature should be at least:

100° F hotter at the converter outlet than at the inlet.

5. If catalytic converter has little or no effect on exhaust temperature, the core may be contaminated.

NOTE: If exhaust temperature exceeds 450° F, the engine may be running too lean. Repair the lean running condition and recheck exhaust temperature before condemning the catalytic converter.