Chapter 18 Diagnosis and Repair of the Emission Control and Exhaust Systems 393
Copyright by Goodheart-Willcox Co., Inc.
by a rise in the exhaust emissions, especially hydrocarbons
(HC). Also, a plugged or inoperative converter will be much
cooler than a normally operating converter.
In some cases, the muffl er can become plugged with
soot or other exhaust debris, but this problem is rare.
Usually, a muffl er that runs cool enough to build up this
level of deposits will corrode and leak before restriction
becomes a problem. Another problem is a clogged tail-
pipe from a restriction placed or wedged in the pipe or
by a collapsed section. A collapsed pipe is obvious in
some cases.
On many vehicles, double-wall pipes are used to
reduce exhaust noise. These pipes are composed of two
separate pipes, one inside of the other, often with a layer
of high-temperature plastic between the pipes for addi-
tional noise reduction. Sometimes, the inner wall of a
double-wall pipe will collapse, but the outer pipe remains
unaffected. If all other causes have been eliminated, the
pipe can be probed with a wire after it is removed from
the vehicle. In some cases, the only way that a collapsed
pipe can be defi nitely located is by removing it and cut-
ting it open.
The diverter plate that is part of the heat riser or EFE
system can stick in the closed position. This will cause a
restriction inside of the exhaust manifold. However, the
system passages are designed to allow partial exhaust fl ow
even when closed. A closed plate is more likely to cause
engine overheating, pinging, or fuel system fl ooding. On
some older V-type engines, a stuck heat riser or EFE valve
can cause the exhaust valves to burn on the corresponding
cylinder bank.
Replacing Emissions and Exhaust
Components
Once you have located the source of the problem,
you can begin the process of replacing the defective parts.
Most repairs of the emissions systems are fairly simple
with very few, if any, non-related parts to remove or relo-
cate. While the exhaust system is simple, care must still
be taken when dealing with this system or other problems
may be created.
Evaporative Emissions Canister
Some evaporative emissions canisters have an inter-
nal fi lter that cannot be replaced. If the fi lter cannot be
replaced or if the canister is otherwise defective, the can-
ister must be replaced.
Many canisters are located in the engine compartment.
Others are located near the fuel tank or at the rear quarter
panel. Consult the service information for the location of
the canister.
After locating the canister, remove the vacuum and
electrical connectors. Be careful to mark any vacuum hoses
if they are of the same size. Then, remove the mounting
brackets and remove the canister. Compare the old and
new canisters. Install the new canister by placing it in the
bracket and reinstalling the vacuum hoses and electrical
connectors.
Figure 18-31. Some parts of the exhaust system are more susceptible to restrictions than others. The colored areas indicate the most
frequent locations for exhaust restrictions. (Chrysler)
Converter
air injector tube
Upper
heat shield
Rear
exhaust
pipe
Muffler
Front
exhaust
pipe
Lower
heat shield
Dual-bed
catalytic
converter
Tailpipe
Most frequent
location of
exhaust restrictions
U-bolt
clamp