Chrysler Concorde 1993 Service Manual page 455

11 - 2 EXHAUST SYSTEM AND INTAKE MANIFOLD
CAUTION: Due to exterior physical similarities of
some catalytic converters with pipe assemblies, ex-
treme care should be taken with replacement parts.
There is internal converter differences required in
some parts of the country (particularly California
vehicles).
EXHAUST GAS RECIRCULATION (EGR)
SYSTEM
To assist in the control of oxides of nitrogen (NOx)
in engine exhaust, all engines are equipped with an
exhaust gas recirculation (EGR) system. The use of
inert exhaust gas to dilute incoming air/fuel mix-
tures lowers peak flame temperature during combus-
tion, thus limiting the formation of NOx.
Exhaust gases are routed through a tube from the
exhaust manifold to the intake manifold adaptor.
Where they are metered by the EGR valve into the
intake system. REFER TO SECTION 25, EMISSION
CONTROL SYSTEMS FOR A COMPLETE DE-
SCRIPTION, DIAGNOSIS AND THE PROPER SER-
VICE PROCEDURES.
HEAT SHIELDS
Heat shields (Fig. 2) are needed to protect both the
car and the environment from the high temperatures
developed in the vicinity of the catalytic converters
and muffler. Each catalytic converter has a intergal
heat shield attached to it and are not to be removed.
Refer to Body and Sheet Metal, Group 23 for ser-
vice procedures.
CAUTION: Avoid application of rust prevention
compounds or undercoating materials to exhaust
system floor pan heat shields on cars if equipped.
Light overspray near the edges is permitted. Appli-
cation of coating will greatly reduce the efficiency
of the heat shields resulting in excessive floor pan
temperatures and objectionable fumes.
The combustion reaction caused by the catalyst re-
leases additional heat in the exhaust system. Caus-
ing temperature increases in the area of the reactor
under severe operating conditions. Such conditions
can exist when the engine misfires or otherwise does
not operate at peak efficiency. Do not remove spark
plug wires from plugs or by any other means short
out cylinders if exhaust system is equipped with cat-
alytic converter. Failure of the catalytic converter
can occur due to temperature increases caused by un-
burned fuel passing through the converter.
The use of the catalysts also involves some non-au-
tomotive problems. Unleaded gasoline must be used
to avoid poisoning the catalyst core. Do not allow en-
gine to operate above 1200 RPM in neutral for ex-
tended periods over 5 minutes. This condition may
result in excessive exhaust system/floor pan temper-
atures because of no air movement under the vehicle.
Fig. 2 Muffler Heat Shield Installation