Lumina V6-191 3.1L VIN T MFI (1993)
Catalytic Converter: Testing and Inspection
Exhaust Backpressure Test Gage Hook-up
Proper diagnosis for a restricted exhaust system is essential before any components are replaced. Either of the following procedures may be used for
diagnosis, depending upon engine or tool used:
CHECK AT AIR PIPE: (when equipped)
1. Remove the rubber hose at the exhaust manifold AIR pipe check valve. Remove check valve.
2. Connect exhaust backpressure kit (with air adapter) J 35314-A.
3. Insert the adapter into the exhaust manifold AIR pipe.
CHECK AT OXYGEN SENSOR:
1. Carefully remove heated oxygen sensor.
2. Install exhaust backpressure gage J 35314-A in place of heated oxygen sensor (refer to illustration).
3. After completing test described below, coat threads of heated oxygen sensor with anti-seize compound P/N 5613695 or equivalent prior to
re-installation.
DIAGNOSIS:
1. With the engine idling at normal operating temperature, observe the exhaust system backpressure reading on the gage. Reading should not exceed
8.6 kPa (1.25 psi).
2. Increase engine speed to 2000 RPM and observe gage. Reading should not exceed 20.7 kPa (3 psi).
3. If the backpressure at either speed exceeds specification, a restricted exhaust system is indicated.
4. Inspect the entire exhaust system for a collapsed pipe, heat distress, or possible internal muffler failure.
5. If there are no obvious reasons for the excessive backpressure, the catalytic converter is suspected to be restricted and should be replaced using
current recommended procedures.
