Grand Caravan FWD V6-3.3L VIN 3 Flex Fuel (2002)
Catalytic Converter: Description and Operation
DESCRIPTION
The toe board three-way catalytic converter is connected 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.
The exhaust flex-joint coupling is used to secure the catalytic converter to the exhaust manifold. The flex-joint has four bolts, four flag nuts and a
gasket 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
converted into water (H20) and carbon dioxide (C02). Oxides of Nitrogen (NOx) are converted into elemental 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 "punch through."
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 somewhat related to proper operation, oxygen
