1988 JEEP CHEROKEE ignition

Fig. 2: 4.0L & 4.2L Timing Marks & Firing Order
Magnetic probe located at 9.5 degrees ATDC on 4.2L.
IGNITION TIMING (4.0L)
Information not available from manufacturer.
IGNITION TIMING (4.2L)
NOTE: Engines are equipped with a receptacle for a magnetic probe
timing light, located 9.5 degrees ATDC. Do not use this
location to check timing with a conventional light, use a
magnetic probe timing light.
Standard Timing Procedure
1) Apply parking brake, and place transmission in Neutral
(Park for automatic transmissions). Operate engine to normal operating\
temperature. Turn ignition off. Install timing light.
2) Connect tachometer. Disconnect and plug vacuum hose at
distributor. Disconnect vacuum switch assembly wire connector, located
on top of valve cover. Start engine and increase engine speed to 1600
RPM.
3) Compare timing to specification. See
IGNITION TIMING SPECIFICATIONS table. To adjust timing, loosen
distributor clamp bolt and turn distributor. Recheck timing after
clamp bolt is tightened.
Alternate Timing Procedure
1) Apply parking brake and place transmission in Neutral
(Drive for automatic transmissions). Operate engine to obtain normal
operating temperature. Turn ignition off. Install timing light.
2) Disconnect and plug vacuum switch hose (Red and Black

wires connected to switch). Disconnect distributor vacuum advance hose
and connect hose to vacuum switch. Disconnect wire connector from
knock sensor, located in cylinder head.
3) Using a jumper wire, ground knock sensor wire connector to
engine block. Start engine. With engine at idle speed (solenoid
energized), check timing. Adjust timing to one degree more than
specification (if required). See Emission Control Label.
IGNITION TIMING SPECIFICATIONS (DEGREES BTDC@RPM) - 4.2L









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Application Man. Trans. Auto. Trans.
50 State ............. 9 @ 1600 ............... 9 @ 1600
High Altitude ........ 16 @ 1600 ............. 16 @ 1600









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HOT (SLOW) IDLE RPM
4.0L
1) Apply parking brake and place transmission in Neutral
(Drive for automatic transmissions). Operate engine to normal
operating temperature. Turn ignition off.
2) Ensure all accessories are off. Connect positive
tachometer lead to terminal "D1-1" and negative lead to "D2-7" of
diagnostic connectors. See Fig. 3. Disconnect air stepper motor
connector and TPS wiring connector. See Fig. 4.
Fig. 3: Diagnostic Connector Terminal Identification
Courtesy of Chrysler Motors.

Fig. 4: Installing Air Stepper Motor Exerciser
Courtesy of Chrysler Motors.
3) Install Air Stepper Motor Exerciser (Ele.CT01) on the air\
stepper motor connector. See Fig. 4. Install the Red terminal of the
air stepper exerciser on the positive battery post and the Black
terminal on the negative battery terminal.
4) Start engine and place stepper motor exerciser switch on
the "LOW" position and note engine RPM. Idle speed should be 750F50
RPM. Disconnect and remove air stepper motor exerciser.
5) If adjustment is required, turn ignition off. Remove the
welch plug from the RPM adjusting screw cavity. See Fig. 5. Turn RPM
adjusting screw inward 2 turns. Start the engine and note engine RPM.

or vehicle fails emissions testing.
IDLE MIXTURE (TACHOMETER (LEAN DROP) PROCEDURE)
NOTE: On 4.2L engines, ensure idle speed and timing are set prior
to adjusting the idle mixture. If mixture adjustment time
exceeds 3 minutes, run engine at 2000 RPM in Neutral for one
minute, and resume adjustment. On 4.0L engines, idle mixture
adjustment is not possible.
4.2L
1) Remove carburetor and locate roll pins blocking idle
mixture screws. Drill through throttle body on closed end of roll pin
hole. Drive pins out with punch. Reinstall carburetor. Install
tachometer.
2) Operate engine to normal operating temperature, and adjust
curb idle speed. Place automatic transmission selector in Drive
(Neutral for manual transmissions). Turn mixture screws inward until
RPM drops. Turn screws outward until highest RPM is reached.
3) Turn mixture screws inward to obtain the correct decrease
in RPM. See LEAN DROP (RPM) table. Adjust both screws equally. When
mixture is correctly adjusted, replace roll pin to block adjustment
screws.
NOTE: If final RPM differs more than 30 RPM from specified curb
idle speed, reset curb idle, and repeat mixture adjustment.
LEAN DROP (RPM) TABLE









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Application Man. Trans. Auto. Trans.
4.2L .................... 50 ........................ 50









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THROTTLE POSITION SENSOR (TPS)
NOTE: Adjustment of TPS only applies to the 4.0L models. It may be
necessary to remove throttle body from intake manifold, to
access sensor wiring harness.
Checking & Adjusting - 4.0L (Automatic Transmission)
1) Locate the square TPS connector. Note connector terminal
identification stamped on the back of the connector. Turn ignition on.
2) Connect voltmeter through back of wiring harness
connector. Connect negative voltmeter lead to terminal "D" and
positive voltmeter lead to terminal "A" to check input voltage. DO NOT
disconnect TPS connector.
3) Hold throttle plate closed against idle stop and note
voltage. Input voltage should be approximately 5 volts. Disconnect
voltmeter positive lead and connect to terminal "B" to measure output
voltage.
4) With throttle plate closed, measure the output voltage.
The output voltage should be approximately 4.2 volts. If output
voltage is not within specification, loosen TPS retaining screws.
5) Partially tighten one retaining screw. Rotate TPS to
obtain correct output voltage. Tighten retaining screws once correct
voltage is obtained.
Checking & Adjusting - 4.0L (Manual Transmission)
1) Turn ignition on. Connect voltmeter through back of wiring
harness connector. Connect negative voltmeter lead to terminal
"B" and positive voltmeter lead to terminal "A". DO NOT disconnect TPS
connector.

2) Hold throttle plate in the closed throttle position
against idle stop and note input voltage reading. Input voltage should
be approximately 5.0 volts.
3) Disconnect positive lead from terminal "A" and connect to
terminal "C" to check output voltage. Output voltage should be checked
with throttle plates fully closed.
4) Output voltage should be approximately 0.8 volts. If
output voltage is not within specification, loosen TPS bottom
retaining screw and pivot sensor for a large adjustment or top
retaining screw for a fine adjustment.
5) Adjust sensor to obtain correct output voltage. Tighten
retaining screws. Remove voltmeter.
COLD (FAST) IDLE RPM
4.2L
Disconnect and plug EGR valve vacuum hose. With engine
running at normal operating temperature, place fast idle screw on
second step of fast idle cam and against shoulder of high step. Turn
screw to adjust fast idle speed.
FAST IDLE SPEED (RPM) TABLE









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Application Man. Trans. Auto. Trans.
4.2L ................... 1700 ..................... 1700









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AUTOMATIC CHOKE SETTING
Choke coil cover is riveted in place and no adjustment is
necessary or possible.
SERVICING
EMISSION CONTROL
See EMISSIONS section.
SPECIFICATIONS
IGNITION
Distributor
All vehicles use a Motorcraft breakerless solid state
distributor.
PICK-UP COIL RESISTANCE TABLE - OHMS @ 75
F (24C)








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Application Specification
All Models ....................................... 400-800









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TOTAL SPARK ADVANCE TABLE @ 2000 RPM








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Application W/ Vac. Advance W/O Vac. Advance
4.0L ................ N/A .......................... N/A
4.2L ............... 30.5
 ................... 7.5-12.5

(1) - Information not available from manufacturer.








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IGNITION COIL
IGNITION COIL OUTPUT TABLE @ 1000 RPM








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Application Output
All Models .................................. 24KV Minimum









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IGNITION COIL RESISTANCE TABLE








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Temperature Primary Ohms Secondary Ohms
75
F (24C) .......... 1.13-1.23 ............. 7700-9300
200F (93C) ............ 1.5 ................... 12,000








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FUEL SYSTEM
CARBURETORS & FUEL INJECTION TABLE








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Application Model
4.0L ................................................ MPFI
4.2L ................................... Carter BBD 2-Bbl.









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BATTERY
BATTERY SPECIFICATIONS TABLE








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Application Cold Cranking Reserve Capacity
** ( 1) Amps Minutes
Standard ................ 421 ....................... 75
Optional ................ 452 ....................... 81
( 1) - At 0
F (-18C).








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STARTER
All models equipped with Mitsubishi starters.
STARTER SPECIFICATIONS TABLE









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Application Volts Amps Test RPM
All Models ...... 11.22 .......... 80 ........... 2500









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ALTERNATOR
All models use Delco-Remy solid state alternators with
internal voltage regulator.
ALTERNATOR SPECIFICATIONS TABLE









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Application Field Current Rated

TU RN S IG NALS & H AZA R D F LA SH ER S

1988 J e ep C hero ke e
1988 Turn Signal & Hazard Light Systems
JEEP
DESCRIPTION
Turn signals and hazard flashers systems use a common turn
signal/hazard light switch assembly mounted within upper steering
column housing.
FLASHER LOCATIONS
Hazard
Mounted on fuse block.
Turn Signal
Mounted on fuse block.
TROUBLE SHOOTING
NOTE: Following trouble shooting is only information available
from manufacturer.
Hazard Lights (Comanche, Cherokee & Wagoneer)
If lights do not come on with hazard switch turned on, check
hazard/stop light fuse by operating stop lights. If fuse is okay,
check turn signal flasher, turn signal/hazard switch, and related
wiring. If only one hazard light does not work, check bulb.
Turn Signals (Comanche, Cherokee & Wagoneer)
If all turn signals do not work, check turn/back-up light
fuse by operating back-up lights. If fuse is okay, check turn signal
flasher, turn signal/hazard switch, and related wiring. If only one
turn signal does not work, check bulb.
TESTING
NOTE: Following trouble shooting is only information available
from manufacturer.
Hazard Indicators (Wrangler)
1) Turn ignition and hazard warning switch "ON". Check for
pulsating voltage at Light Blue (left indicator) and Dark Blue (right\
indicator) wires. If voltage is present, go to next step. If voltage
is not present, replace turn signal switch.
2) Remove bulbs for turn signal indicators. Measure
resistance across bulb terminals. If resistance is zero ohms, replace
light bulb(s). If resistance readings are not zero ohms, go to next
step.
3) Check for pulsating voltage at battery side of bulb
sockets. If voltage is present, go to next step. If voltage is not
present, repair open circuit between socket and turn signal switch
steering column connector.
4) Turn ignition off and check resistance on ground side of
bulb sockets. If resistance is zero ohms, hazard indicator circuit is
okay. If resistance reading is not zero ohms, repair open in ground
circuit.
Hazard Lights (Wrangler)

1) Check operation of stop lights. If stop lights come on, go
to next step. If not, check hazard/stop light fuse. If fuse is okay,
check for voltage on battery side of hazard/stop light fuse. If
voltage is not present, repair open circuit between fusible link and
fuse block.
2) Remove hazard flasher and check for voltage on battery
side of hazard flasher at fuse block. If voltage is present, go to
next step. If voltage is not present, repair open circuit to fuse
block.
3) Measure resistance across turn signal flasher terminals.
If resistance across flasher is zero ohms, replace flasher. If
resistance is other than zero ohms, install flasher and turn ignition
on.
4) Check for voltage at Brown wire of turn signal switch
steering column connector. If voltage is present, go to next step. If
voltage is not present, repair open circuit between flasher and turn
signal switch connector.
5) Turn hazard warning switch "ON". Check for pulsating
voltage at Light Blue, Dark Blue, Yellow, and Dark Green wires. If
voltage is present, hazard light circuit is okay. If voltage is not
present, replace turn signal switch.
Turn Signals (Wrangler)
1) Turn ignition on and check operation of back-up lights. If
lights come on, go to step 3). If back-up lights do not come on, check
turn signal/back-up light fuse.
2) If fuse is okay, check for voltage at battery side of turn
signal/back-up light fuse. If voltage is not present, repair open
circuit between fuse block and ignition switch. If voltage is present,
go to next step.
3) Remove turn signal flasher and measure resistance across
flasher terminals. If resistance across flasher is zero ohms, replace
turn signal flasher. If flasher is okay, install flasher and turn
ignition on.
4) Check for voltage on battery side of flasher at fuse
block. If voltage is present, go to next step. If voltage is not
present, repair open circuit to fuse block.
5) Disconnect turn signal switch at steering column
connector. Place turn signal switch in left turn position and measure
resistance between Yellow and Purple wires. If resistance across wires
is zero ohms, replace turn signal switch. If resistance is other than
zero ohms, go to next step.
6) Place turn signal switch in right turn position and
measure resistance between Dark Green and Purple wires. If resistance
across wires is zero ohms, replace turn signal switch. If resistance
is other than zero ohms, turn signal circuit is okay.
Turn Signal Indicators (Wrangler)
1) Turn ignition on. Place turn signal switch in left turn
position and check for pulsating voltage at Light Blue wire. If
voltage is present, go to next step. If voltage is not present,
replace turn signal switch.
2) Place turn signal switch in right turn position and check
for pulsating voltage at Dark Blue wire. If voltage is not present,
replace turn signal switch. If voltage is present, go to next step.
3) Remove bulbs from turn signal indicators. Measure
resistance across bulb terminals. If resistance is zero ohms, replace
light bulb(s). If resistance readings are not zero ohms, turn ignition\
on.
4) Place turn signal switch in left and right turn position
and check for pulsating voltage at battery side of bulb sockets. If
voltage is present, go to next step. If voltage is not present, repair
open circuit between socket(s) and steering column connector.