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EXHAUST SYSTEM AND INTAKE MANIFOLD
11-1
EXHAUST SYSTEM AND INTAKE MANIFOLD
C O N T E N T S
Page
EXHAUST DIAGNOSIS . .
GENERAL INFORMATION
3
1
SERVICE PROCEDURES
Page
. . . 3
G E N E R A L INFORMATION
INDEX
Page
Catalytic Converter
1
Exhaust G a s Recirculation ( E G R ) .
1
Exhaust System
1
EXHAUST SYSTEM
The basic exhaust system consists of exhaust m a n -
ifolds, exhaust pipe, catalytic converter(s), extension
pipe, heat shields, muffler a n d tailpipe (Fig. 1).
A l l engines have a thermostatic controlled heat
valve i n the exhaust m a n i f o l d for faster w a r m u p and
improved d r i v e a b i l i t y after cold start.
The
exhaust manifolds are equipped w i t h
b a l l
flange
outlets t o assure a t i g h t seal and s t r a i n free
connections. T h e exhaust system must be properly
aligned to prevent stress, leakage and body contact.
I f the system contacts any body panel, i t may am-
plify objectionable noises o r i g i n a t i n g from the engine
or body.
W h e n inspecting a n exhaust system, c r i t i c a l l y i n -
spect for cracked or loose j o i n t s , stripped screw or
bolt threads, corrosion damage and w o r n , cracked or
broken hangers. Replace a l l components t h a t are
badly corroded or damaged. D O N O T attempt t o re-
pair.
W h e n replacement is required, use o r i g i n a l equip-
m e n t parts (or t h e i r equivalent) to assure proper
a l i g n m e n t a n d t o provide acceptable exhaust noise
levels.
CAUTION: Avoid application of rust
prevention
compounds or undercoating materials to exhaust
system floor pan heat shields. Light overspray near
the edges is permitted. Application of coating will
result in excessive floor pan temperatures and ob-
jectionable fumes.
CATALYTIC CONVERTER
The stainless steel catalytic converter body is de-
signed to last t h e life o f the vehicle. Excessive heat
can result i n b u l g i n g or other distortion, b u t exces-
sive heat w i l l not be the f a u l t of t h e converter. A fuel
system, a i r injection system or i g n i t i o n system m a l -
Heat Shields
Manifold Heat Control Valve
Page
. . . 1
. . . 2
function t h a t p e r m i t s u n b u r n e d fuel t o enter the con-
verter w i l l usually cause overheating. I f a converter
is heat-damaged, correct the cause o f the damage a t
the same t i m e t h e converter is replaced. Also, inspect
a l l other components of the exhaust system for heat
damage.
Unleaded gasoline m u s t be used t o avoid contami-
n a t i n g the catalyst core.
HEAT SHIELDS
Heat shields are needed to protect both the vehicle
and the environment from the h i g h temperatures de-
veloped i n the v i c i n i t y of the catalytic converter. The
combustion reaction facilitated by t h e catalyst re-
leases additional heat i n the exhaust system. U n d e r
severe operating conditions, t h e temperature i n -
creases i n t h e area o f the reactor. Such conditions
can exist when the engine misfires or otherwise does
not operate
a t peak efficiency.
D O N O T remove
spark p l u g wires f r o m plugs or b y any other means
short out cylinders. F a i l u r e o f the catalytic converter
can qccur due t o a temperature increase caused b y
u n b u r n e d fuel passing t h r o u g h the converter.
Do not allow the engine to operate a t fast idle for
extended periods (over five minutes). This condition
may result i n excessive temperatures i n the exhaust
system and on the floor p a n .
EXHAUST GAS RECIRCULATION (EGR)
To assist i n t h e control of oxides of nitrogen (NOx)
i n engine exhaust, a l l engines are equipped w i t h a n
exhaust gas r e c i r c u l a t i o n system. The use of exhaust
gas to d i l u t e i n c o m i n g air/fuel m i x t u r e s lowers peak
flame temperatures d u r i n g combustion, thus l i m i t i n g
the formation of NOx.
Exhaust gases are t a k e n from openings i n the ex-
haust gas crossover passage i n the i n t a k e manifold.
Refer to Group 25, Emission Control Systems of t h i s
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