1988 JEEP CHEROKEE check engine

SPARK PLUG CHECK
Faulty or fouled plugs may perform well at idle speed, but at
higher engine speeds, they frequently fail. Faulty plug can exhibit
the following symptoms:
* Poor fuel economy.
* Power loss.
* Decreased engine speed.
* Hard starting.
* Generally poor performance.
Spark plugs also malfunction due to carbon fouling,
excessive electrode air gap, or broken insulators.
SYNC PULSE SIGNAL GENERATOR (STATOR) TEST
NOTE: For this test, an analog voltmeter MUST be used.
1) Insert the positive (+) lead of the voltmeter into the
Blue wire at the distributor connector.
2) Insert the negative (-) voltmeter lead into the Gray/Whit\
e
wire at the distributor connector.
CAUTION: DO NOT remove the distributor connector from distributor.
Insert the voltmeter leads into the backside of the
distributor connector to make contact with the terminals.
3) Set the voltmeter to the 15-Volt D/C scale. Turn ignition
key to "ON".
4) The voltmeter should display approximately 5.0 volts.
5) If no voltage displays, check that the voltmeter leads are
making good contact. If there is still no voltage, go to next step.
6) Remove the ECU and check for voltage at pin "C-16" and
ground with harness connected. If there in still no voltage, proceed
to the next step.
7) Connect Diagnostic Tester M.S. 1700 to the vehicle. Using
the diagnostic tester, perform vehicle test. If voltage is present, go
to the next step.
8) Check for continuity between the Blue wire at the
distributor connector and pin C-16 at the ECU.
9) If there in no continuity, repair harness as necessary.
10) Check for continuity between the Gray/White wire at the
distributor connector and pin C-5 at the ECU.
11) If there is no continuity, repair harness as necessary.
12) Check for continuity between the Black wire at the
distributor connector and ground.
13) If there is no continuity, repair harness as necessary.
14) While observing the voltmeter, crank the engine; the
voltmeter needle should fluctuate back and forth while the engine in
cranking. A fluctuation verifies that the stator in the distributor is
operating properly.
15) If there is no pulse sync, replace the stator. Refer to
REMOVAL & INSTALLATION below in this article.
REMOVAL & INSTALLATION
COOLANT TEMPERATURE SENSOR (CTS)
Removal
1) Drain the cooling system.

system. For testing, see appropriate IGNITION SYSTEM CHECK
flow chart in COMPUTERIZED ENGINE CONTROLS section. For
diagnosis of HEI system, refer to following diagnostic
chart. See Fig. 11.
Fig. 11: Ignition Sys Check (HEI Only), Testing applies to HEI
sys with mechanical weights and vacuum advance.
Courtesy of General Motors Corp.
OVERHAUL

* Cold Climate Operation
* Towing Or Heavily Loading
* Severe Dust Conditions
* Sustained High Speed Operation
* Off-Road Driving
* Hot Weather, Stop-And-Go Driving
* Extensive Idling Conditions (Taxi Or Delivery Type Service)
Normal Service
* Driven More Than 10 Miles Daily
* No Severe Service Operating Conditions
CAMSHAFT TIMING BELT REPLACEMENT INFORMATION (TURBO-DIESEL)
CAUTION: Failure to replace a faulty camshaft timing belt may result
in serious engine damage.
The condition of camshaft drive belts should always be
checked on vehicles which have more than 50,000 miles. Although some
manufacturers do not recommend belt replacement at a specified
mileage, others require it at 60,000-100,000 miles. A camshaft drive
belt failure may cause extensive damage to internal engine components
on most engines, although some designs do not allow piston-to-valve
contact. These designs are often called "Free Wheeling".
Many manufacturers changed their maintenance and warranty
schedules in the mid-1980's to reflect timing belt inspection and/or
replacement at 50,000-60,000 miles. Most service interval schedules
reflect these changes.
Belts or components should be inspected and replaced if any
of the following conditions exist:
* Cracks Or Tears In Belt Surface
* Missing, Damaged, Cracked Or Rounded Teeth
* Oil Contamination
* Damaged Or Faulty Tensioners
* Incorrect Tension Adjustment
SERVICE LABOR TIMES
SERVICE LABOR TIMES TABLE (HOURS)








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( 1) 30,000 60,000
Application Mile Service Mile Service
2.1L (Turbo Diesel)
Automatic Transmission ........... 4.3 ................ 4.5
Manual Transmission .............. 3.6 ................ 3.8
2.5L
Automatic Transmission ........... 5.6 ................ 3.5
Manual Transmission .............. 4.9 ................ 3.5
2.8L
Automatic Transmission ........... 5.8 ................ 3.7
Manual Transmission .............. 5.1 ................ 3.7
4.0L
Automatic Transmission ........... 5.7 ................ 3.6
Manual Transmission .............. 5.0 ................ 3.6
( 1) - Add .8 hr. for vehicles equipped with 4WD.









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the ENGINE PERFORMANCE section.
Fuel filter should be drained whenever "WATER IN FUEL"
warning light glows. Diesel fuel can damage asphalt and
painted surfaces. Always place a drain pan under fuel filter
to collect contaminated fuel. See Fig. 2.
1) Stop vehicle and turn engine off. Attach a long piece
of tubing to drain cock outlet. Place end of drain hose into
drain pan. Open filter assembly vent valve (Black + shaped
knob) and drain cock.
2) Drain approximately 1/2 pint (.24 Liters) from fuel
filter. Close vent valve and drain cock. Start engine and
check for leaks. If "WATER IN FUEL" warning lamp comes on
again, remove water contaminated fuel from fuel lines and
fuel tank.
WARNING: DO NOT bleed fuel lines on hot engine, as high exhaust
temperatures could cause fire. Use care when bleeding fuel
lines, as fuel is under extreme pressure and could penetrate
skin, causing personal injury. Wear safety goggles and
protective clothing when bleeding fuel lines.
CAUTION: DO NOT drain fuel/water separator when engine is running or
hot. Allow engine to cool before draining. Verify that the
WATER IN FUEL light on instrument panel is OFF.
Fig. 3: Locking Crankshaft at TDC
Courtesy of American Motors/Jeep Corp.

PO W ER S TE ER IN G G EN ER AL S ER VIC IN G

1988 J e ep C hero ke e
1988 STEERING
Jeep Power Steering General Servicing
Cherokee, Comanche, Grand Wagoneer, Pickup, Wagoneer,
Wrangler
LUBRICATION
SERVICE INTERVALS
Check fluid at every oil change.
CHECKING FLUID LEVEL
Check fluid level with engine stopped and fluid hot or cold.
Fluid level must be at "FULL-HOT" or "FULL-COLD" mark on dipstick. On
models with remote reservoir, keep fluid level 0.5-1.0" from top of
reservoir with wheels turned fully to left.
RECOMMENDED FLUID TABLE









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Application Part Number
Jeep ............................................. 8993342









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REFILLING & BLEEDING SYSTEM
1) Fill reservoir to correct level. Operate engine until
fluid reaches normal operating temperature. Stop engine. Add fluid (if
necessary). Turn wheels to full left position. Add fluid to reservoir
to fill to "FULL-COLD" mark on dipstick.
2) Start and operate engine at fast idle. Recheck reservoir
level. Add to "FULL-COLD" mark on dipstick. Turn wheels from side to
side without contacting stops. Maintain fluid level just above pump
body.
3) When air is removed, return wheels to straight-ahead
position. Operate engine 2-3 minutes. Stop engine. Road test vehicle.
Recheck fluid level. Level should be at "FULL-HOT" position after
system has stabilized. Add fluid (if necessary). DO NOT overfill.
BELT TENSION (Tension in Lbs. Using Boroughs Tension Gauge)









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Application New Belt Used Belt
Jeep ................ ( 1) 125-155 ............... 90-115
( 1) - Cherokee, Comanche and Wagoneer is 120-140 lbs.









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TROUBLE SHOOTING
Refer to TROUBLE SHOOTING - BASIC PROCEDURES article in the
GENERAL TROUBLE SHOOTING section.
TESTING

PREPARATION
1) With belt tension correct, disconnect power steering pump
pressure hose. Keep hose end raised to prevent fluid loss. Connect
pressure hose of gauge to power steering pump fitting. Connect other
hose from valve side of tester to steering gear inlet.
2) Open valve. Run engine until fluid reaches normal
operating temperature of 170
F (77C). Check fluid level. Add fluid
(if necessary).
PRESSURE TEST
1) Note pressure reading with valve open and engine idling.
Pressure should be 80-125 psi (5.6-8.8 kg/cm).
2) If pressure is above 200 psi (14.1 kg/cm), check hoses
for restrictions and poppet valve (Saginaw gears) for proper assembly.\
3) Close gate valve completely and reopen 3 times. Record
highest reading each time. DO NOT close valve for more than 5 seconds.
If pressure is less than specification, clean or replace flow control
valve in pump. If pressures are still low, replace pump.
4) If readings are within specifications and within 50 psi
(3.5 kg/cm
) of each other, pump is operating properly. Refer to the
PRESSURE TEST SPECIFICATIONS table. If pressures are high, but do not
repeat within 50 psi (3.5 kg/cm
), flow control valve in pump is
sticking. Remove flow control valve. Clean or replace flow control
valve.
5) If pump is within specifications, open valve and turn
steering wheel from right to left stops. Record pressure. DO NOT hold
wheel against stops more than 5 seconds.
6) Pressure should measure the same as specified. See the
PRESSURE TEST SPECIFICATIONS table. If pressure is low, steering gear
is leaking internally and must be overhauled.
7) Turn steering wheel from left to right with engine idling
at 600-800 RPM. See PRESSURE TEST SPECIFICATIONS table.
8) If pressure is low, momentarily close valve. If pressure
is less than specified, pump is faulty. If pressure is within
specification but was low at previous reading, steering gear is
faulty.
PRESSURE TEST SPECIFICATIONS TABLE









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Application Idle: psi (kg/cm) Relief: psi (kg/cm)
Jeep ............... 80-125 (6-9) ............. 1400-1500 (98-105\
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To test crankcase ventilation system, start engine and allow
it to reach normal operating temperature. Make sure engine is idling
at normal curb idle, and perform following checks:
1) Remove PCV valve from its mounting. If valve is
functioning properly, hissing noise will be heard as air passes
through it. Strong vacuum should be felt when your finger is placed
over valve inlet.
2) While finger is over inlet, check for presence of vacuum
leaks in hose line and at all connections. Reinstall PCV valve,
remove crankcase air inlet hose at air cleaner.
3) Loosely hold piece of stiff paper over opening at end of
inlet hose. Paper should be sucked against hose opening with
noticeable force after sufficient time has elapsed for crankcase
pressure to lower (usually about a minute). For final check, stop
engine, remove PCV valve and shake it. Metallic clicking noise should
be heard, indicating valve is free.
4) If system passes both engine running and stopped tests,
it is functioning properly. No further tests are required. If it has
failed either test, replace appropriate components and retest. If it
does not pass on second try, clean system.
MAINTENANCE
Engine may idle slow or rough due to clogged ventilator
valve or system. Therefore, never adjust carburetor idle without
first checking valve and system.
If ventilator valve or system becomes clogged, all crankcase
ventilation will stop, and serious engine damage could result.
Although following manufacturers' service procedures give
specific intervals, it is recommended the crankcase ventilation
system be checked more frequently if vehicle is operated under severe
conditions (extreme dust, prolonged idling, trailer hauling or short
trips in cold weather).
PCV VALVE
Replace PCV valve every 30,000 miles. Valve is located on
rocker arm cover of 4-cylinder, 6-cylinder and V6 models and on
intake manifold of V8 models.
FILTER ELEMENT
Clean filter element every 30,000 miles. Filter is located
inside air cleaner of 4-cylinder, 6-cylinder and V6 models and in oil
filler cap of V8 models.

HALOGEN BULBS
Halogen bulbs contain pressurized gas which may explode if
overheated. DO NOT touch glass portion of bulb with bare hands. Eye
protection should be worn when handling or working around halogen
bulbs.
OIL FILTER
CAUTION: The engine oil filter mount has metric threads. Use of a
filter with improper threads can result in oil leakage and
possible engine damage. Look for M20 x 1.5 symbol on the
filter.
RADIATOR CAP
CAUTION: Always disconnect the fan motor when working near the
radiator fan. The fan is temperature controlled and could
start at any time even when the ignition key is in the OFF
position. DO NOT loosen or remove radiator cap when cooling
system is hot.
RADIATOR FAN
Keep hands away from radiator fan. Fan is controlled by a
thermostatic switch which may come on or run for up to 15 minutes even
after engine is turned off.
WHEEL & TIRE WARNINGS
CAUTION: Replacing original tires with different size tires may
result in false speedometer and odometer indications. Check
with dealer before using different size tires on vehicle.
CAUTION: Ensure all 4 wheels on vehicle have same tire size, type
and circumference in order to provide proper vehicle
handling. DO NOT mix radial-ply with bias-ply or
bias-belted tires. On 4WD vehicles, if tire size, type and
circumference on all 4 wheels are not the same, gear
shifting will be adversely affected and can damage transfer
case.
CAUTION: Temporary-use spare tires are for emergency use only. DO
NOT drive vehicle faster than 50 MPH or more than 100 miles
when using spare tire. DO NOT operate vehicle in 4WD mode
when using spare tire, as damage to transfer case can
result. Temporary-use spare tires have a total tread life
of 3,000 miles.
SERVICE POINT LOCATIONS