1994 JEEP CHEROKEE Service Repair Manual

ENGINE SPECIFICATIONS (CONT.)
9 - 88 4.0L ENGINEJ

ENGINE SPECIFICATIONS (CONT.)
TORQUE SPECIFICATIONS
J4.0L ENGINE 9 - 89

EXHAUST SYSTEM AND INTAKE MANIFOLD
CONTENTS
page page
EXHAUST SYSTEM....................... 1
EXHAUST SYSTEM DIAGNOSIS............ 2SERVICE PROCEDURES................... 3
TORQUE SPECIFICATIONS................ 10
EXHAUST SYSTEM
GENERAL INFORMATION
The basic exhaust system consists of an engine ex-
haust manifold, exhaust pipe with oxygen sensor,
catalytic converter, exhaust heat shield(s), muffler
and exhaust tailpipe (Fig. 1).
The exhaust system uses a single muffler with a
single monolithic-type catalytic converter.
The 4.0L engines use a seal between the engine ex-
haust manifold and exhaust pipe to assure a tight
seal and strain free connections.
The exhaust system must be properly aligned to
prevent stress, leakage and body contact. If the sys-tem contacts any body panel, it may amplify objec-
tionable noises originating from the engine or body.
When inspecting an exhaust system, critically in-
spect for cracked or loose joints, stripped screw or
bolt threads, corrosion damage and worn, cracked or
broken hangers. Replace all components that are
badly corroded or damaged. DO NOT attempt to re-
pair.
When replacement is required, use original equip-
ment parts (or their equivalent). This will assure
proper alignment and provide acceptable exhaust
noise levels.
CAUTION: Avoid application of rust prevention
compounds or undercoating materials to exhaust
system floor pan exhaust heat shields. Light overs-
pray near the edges is permitted. Application of
coating will result in excessive floor pan tempera-
tures and objectionable fumes.
CATALYTIC CONVERTER
The stainless steel catalytic converter body is de-
signed to last the life of the vehicle. Excessive heat
can result in bulging or other distortion, but exces-
sive heat will not be the fault of the converter. If un-
burned fuel enters the converter, overheating may
occur. If a converter is heat-damaged, correct the
cause of the damage at the same time the converter
is replaced. Also, inspect all other components of the
exhaust system for heat damage.
Unleaded gasoline must be used to avoid contami-
nating the catalyst core.
EXHAUST HEAT SHIELDS
Exhaust heat shields are needed to protect both the
vehicle and the environment from the high tempera-
tures developed by the catalytic converter. The cata-
lytic converter releases additional heat into the
exhaust system. Under severe operating conditions,
the temperature increases in the area of the con-
Fig. 1 Typical Exhaust System
JEXHAUST SYSTEM AND INTAKE MANIFOLD 11 - 1

verter. Such conditions can exist when the engine
misfires or otherwise does not operate at peak effi-
ciency.
DO NOT remove spark plug wires from plugs or by
any other means short out cylinders. Failure of the
catalytic converter can occur due to a temperatureincrease caused by unburned fuel passing through
the converter.
DO NOT allow the engine to operate at fast idle for
extended periods (over 5 minutes). This condition
may result in excessive temperatures in the exhaust
system and on the floor pan.
EXHAUST SYSTEM DIAGNOSIS
11 - 2 EXHAUST SYSTEM AND INTAKE MANIFOLDJ

SERVICE PROCEDURES
INDEX
page page
Catalytic Converter........................ 5
Engine Exhaust ManifoldÐ2.5L Engine......... 7
Engine Exhaust ManifoldÐ4.0L Engine......... 7
Exhaust PipeÐXJ Vehicles.................. 3
Exhaust PipeÐYJ Vehicles.................. 4Intake ManifoldÐ2.5L Engine................ 8
Intake ManifoldÐ4.0L Engine................ 9
Muffler and Exhaust TailpipeÐXJ Vehicles...... 5
Muffler and Exhaust TailpipeÐYJ Vehicles...... 6
EXHAUST PIPEÐXJ VEHICLES
WARNING: IF TORCHES ARE USED WHEN WORK-
ING ON THE EXHAUST SYSTEM, DO NOT ALLOW
THE FLAME NEAR THE FUEL LINES.
REMOVAL
(1) Raise and support the vehicle.
(2) Saturate the bolts and nuts with heat valve lu-
bricant (Fig. 1). Allow 5 minutes for penetration.
(3) Remove the oxygen sensor from the exhaust
pipe (Fig. 2).
(4) Disconnect the exhaust pipe from the engine
exhaust manifold. Discard the seal (4.0L engine,
only).
(5) Support the transmission and remove the
transmission support crossmember.
(6) Remove the clamp nuts and clamp (Fig. 3). To
remove the exhaust pipe from the catalytic converter,apply heat until the metal becomes cherry red. Dis-
connect the exhaust pipe from the catalytic converter
(Fig. 3). Remove the exhaust pipe.
CLEANING
Clean the mating surfaces of the engine exhaust
manifold flange and the exhaust pipe.
Fig. 1 Exhaust Pipe-to-Engine Exhaust Manifold
Nuts
Fig. 2 Oxygen Sensor
Fig. 3 Exhaust Pipe-to-Catalytic Converter
Connection
JEXHAUST SYSTEM AND INTAKE MANIFOLD 11 - 3

INSTALLATION
(1) Assemble exhaust pipe to manifold and cata-
lytic converter loosely to permit proper alignment of
all parts.
(2) Use a new clamp at the exhaust pipe to cata-
lytic converter connection and tighten the nuts to 61
NzIm (45 ft. lbs.) torque.
(3) Connect the exhaust pipe to the engine exhaust
manifold using new nuts. Install a new seal between
the exhaust manifold and the exhaust pipe (4.0L en-
gine, only). Tighten the nuts to 31 Nzm (23 ft. lbs.)
torque (Fig. 1).
(4) Align the transmission support crossmember to
the exhaust pipe (Fig. 3) and position on the sill.
Tighten the crossmember-to-sill bolts to 41 Nzm (30
ft. lbs.) torque. Remove the support from the trans-
mission.
(5) Coat the oxygen sensor with anti-seize com-
pound. Install the sensor and tighten the nut to 48
Nzm (35 ft. lbs.) torque.
(6) Lower the vehicle.
(7) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed.
EXHAUST PIPEÐYJ VEHICLES
WARNING: IF TORCHES ARE USED WHEN WORK-
ING ON THE EXHAUST SYSTEM, DO NOT ALLOW
THE FLAME NEAR THE FUEL LINES.
REMOVAL
(1) Raise and support the vehicle.
(2) Saturate the bolts and nuts with heat valve lu-
bricant (Fig. 4). Allow 5 minutes for penetration.
(3) Remove the oxygen sensor from the exhaust
pipe (Fig. 2).
(4) Disconnect the exhaust pipe from the engine
exhaust manifold. Discard the seal (4.0L engine,
only).
(5) Remove the clamp nuts and clamp (Fig. 5). To
remove the exhaust pipe from the catalytic converter,
apply heat until the metal becomes cherry red. Dis-
connect the exhaust pipe from the catalytic converter
and slide the pipe out of the transmission torque arm
insulator (Fig. 5). Remove the exhaust pipe.
CLEANING
Clean the mating surfaces of the engine exhaust
manifold flange and the exhaust pipe.
INSTALLATION
(1) Slide the exhaust pipe into the transmission
torque arm insulator and onto the catalytic converter
(Fig. 5).
(2) Connect the exhaust pipe to the engine exhaust
manifold using new nuts. Install a new seal betweenthe exhaust manifold and the exhaust pipe (4.0L en-
gine, only). DO NOT tighten the nuts at this time.
(3) Align the exhaust pipe.
(4) Use a new clamp at the exhaust pipe to cata-
lytic converter connection and tighten the nuts to 61
Nzm (45 ft. lbs.) torque.
(5) Tighten the exhaust pipe-to-engine exhaust
manifold nuts to 31 Nzm (23 ft. lbs.) torque.
(6) Coat the oxygen sensor with anti-seize com-
pound. Install the sensor and tighten the nut to 48
Nzm (35 ft. lbs.) torque.
(7) Lower the vehicle.
(9) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed.
Fig. 4 Exhaust Pipe-to-Engine Exhaust Manifold
Nuts
Fig. 5 Exhaust Pipe-to-Catalytic Converter
ConnectionÐYJ Vehicles
11 - 4 EXHAUST SYSTEM AND INTAKE MANIFOLDJ

CATALYTIC CONVERTER
WARNING: IF TORCHES ARE USED WHEN WORK-
ING ON THE EXHAUST SYSTEM, DO NOT ALLOW
THE FLAME NEAR THE FUEL LINES.
REMOVAL
(1) Raise and support the vehicle.
(2) Remove the clamp from the catalytic converter
and muffler connection (Fig. 6). Remove the clamp
from the catalytic converter and exhaust pipe connec-
tion (Figs. 3 and 5).
(3) Heat the catalytic converter connections with
an oxyacetylene torch until the metal becomes cherry
red.
(4) While the metal is still cherry red, twist the
muffler assembly back and forth to separate it from
the catalytic converter.
(5) While the metal is still cherry red, disconnect
the exhaust pipe from the catalytic converter (Figs. 3
and 5).
INSTALLATION
(1) Connect the catalytic converter to the exhaust
pipe (Figs. 3 and 5). Use a new clamp and tighten
the nuts to 61 Nzm (45 ft. lbs.) torque.
(2) Install the muffler onto the catalytic converter
until the alignment tab is inserted into the align-
ment slot.
(3) Install a new clamp at the muffler and cata-
lytic converter connection (Fig. 6). Tighten the clamp
nuts to 61 Nzm (45 ft. lbs.) torque.
(4) Lower the vehicle.
(5) Start the engine and inspect for exhaust leaks
and exhaust system contact with the body panels.
Adjust the alignment, if needed.
MUFFLER AND EXHAUST TAILPIPEÐXJ VEHICLES
All original equipment exhaust systems are manu-
factured with the exhaust tailpipe welded to the muf-
fler. Service replacement mufflers and exhaust
tailpipes are either clamped together or welded to-
gether.
WARNING: IF TORCHES ARE USED WHEN WORK-
ING ON THE EXHAUST SYSTEM, DO NOT ALLOW
THE FLAME NEAR THE FUEL LINES.
REMOVAL
(1) Raise and support the vehicle.
(2) Remove the front muffler clamp from the cata-
lytic converter and muffler connection (Fig. 6).
(3) Remove the rear exhaust tailpipe hanger clamp
(Fig. 7) and remove the exhaust tailpipe from the
front exhaust tailpipe hanger (Fig. 8).
(4) Heat the catalytic converter-to-muffler connec-
tion with an oxyacetylene torch until the metal be-
comes cherry red.
(5) While the metal is still cherry red, remove the
exhaust tailpipe/muffler assembly from the catalytic
converter.
(6) Remove the exhaust tailpipe from the muffler:
²To remove an original equipment exhaust tailpipe/
muffler combination, cut the exhaust tailpipe close to
the muffler. Collapse the part remaining in the muf-
fler and remove.
²To remove a service exhaust tailpipe/muffler com-
bination, apply heat until the metal becomes cherry
Fig. 6 Catalytic Converter-to-Muffler Connection
Fig. 7 Rear Exhaust Tailpipe Hanger Clamp
JEXHAUST SYSTEM AND INTAKE MANIFOLD 11 - 5