SPECIAL TOOLS
EXHAUST SYSTEM
CATALYTIC CONVERTER
DESCRIPTION
The toe board three-way catalytic converter is con-
nected to the exhaust manifold by the use of flex
joint and a gasket. The outlet connects to the muffler
inlet pipe and is secured with a band type clamp
(Fig. 1).
The exhaust flex-joint coupling (Fig. 3) is used to
secure the catalytic converter to the exhaust manifold.
The flex-joint has four bolts, four flag nuts and a gas-
ket that are separate parts from the exhaust flex-joint.
The flex-joint is welded to the catalytic converter.
CAUTION: When servicing, care must be exercised
not to dent or bend the bellows or bellows cover of
the flex-joint. Should this occur, the flex-joint will
eventually fail and require the catalytic converter be
replaced.
OPERATION
The three-way catalytic converter simultaneously
converts three exhaust emissions into harmless
gases. Specifically, HC and CO emissions are con-
verted into water (H2O) and carbon dioxide (CO2).
Oxides of Nitrogen (NOx) are converted into elemen-
tal Nitrogen (N) and water. The three-way catalyst is
most efficient in converting HC, CO and NOx at the
stoichiometric air fuel ratio of 14.7:1.
The oxygen content in a catalyst is important for
efficient conversion of exhaust gases. When a high
oxygen content (lean) air/fuel ratio is present for an
extended period, oxygen content in a catalyst can
reach a maximum. When a rich air/fuel ratio is
present for an extended period, the oxygen content in
the catalyst can become totally depleted. When this
occurs, the catalyst fails to convert the gases. This is
known as catalyst
9punch through.9
Catalyst operation is dependent on its ability to
store and release the oxygen needed to complete the
emissions-reducing chemical reactions. As a catalyst
deteriorates, its ability to store oxygen is reduced.
Since the catalyst’s ability to store oxygen is some-
what related to proper operation, oxygen storage can
be used as an indicator of catalyst performance.
Refer to the appropriate Diagnostic Information for
diagnosis of a catalyst related Diagnostic Trouble
Code (DTC).
Back Pressure Test Adapter - CH8519
Pressure Transducer CH7063
DRB III & PEP Module - OT-CH6010A
Fig. 3 Flex-joint
1 - FLANGE
2 - END CAPS
3 - CATALYTIC CONVERTER
4 - FLEXIBLE BELLOWS
11 - 4
EXHAUST SYSTEM
RS
EXHAUST SYSTEM (Continued)