98 Jeep Cherokee Performance Tune Download

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Online Manual Jeep >Jeep Cherokee >Jeep Cherokee (XJ) >1984 - 1991 > TUNE-UP - 6-CYL

TUNE-UP - 6-CYL

1988 Jeep Cherokee

Our performance chips & power programmers let you tune the engine in your 2000 Jeep Cherokee for more performance, towing power, or increased fuel economy. Rusty's Off-Road offers an enormous variety of Jeep performance parts that improve horsepower, torque, and throttle response. Rusty's offers intake kits, cold air intake systems, throttle body spacers, exhaust systems, headers, motor and tranny mounts, programmers, clutches, throttle bodies, air filters, and much more. Rusty's offers performance products for Jeep XJ Cherokee, JK Wrangler, TJ.

1987-88 TUNE-UP

Timing is adjustable on 1984-86 vehicles only. On 1987-98 vehicles, the timing is controlled by the Powertrain Control Module (PCM) and is not adjustable. On 1984-86 models, timing should be checked at each tune-up and any time components are replaced in the ignition system. TUNE-UP - 6-CYL 1988 Jeep Cherokee 1987-88 TUNE-UP Jeep 6 Cylinder Tune-Up. Cherokee, Comanche, Wagoneer, Wrangler. ENGINE IDENTIFICATION. Engine can be identified by the fourth character of engine Build Date Code number, located on a tag attached to right side of block between No. 2 and 3 cylinders. The same code letter is also the fourth character in the Vehicle.

Jeep 6 Cylinder Tune-Up

Cherokee, Comanche, Wagoneer, Wrangler

IDENTIFICATION

ENGINE IDENTIFICATION

Engine can be identified by the fourth character of engine Build Date Code number, located on a tag attached to right side of block between No. 2 and 3 cylinders.

The same code letter is also the fourth character in the Vehicle Identification Number (VIN), located at top left corner of dashboard.

ENGINE CODE TABLE

Engine Code

4.0L (242') MPFI M

4.2L (258') 2-Bbl C

TUNE-UP NOTES

NOTE: When performing tune-up procedures described in this

article, these notes and precautions must be followed.

Due to late changes and corrections, always refer to Emission Control Label in engine compartment before attempting tune-up. If manual and label specifications differ, use label specifications.

When performing tune-up on vehicles equipped with a catalytic converter, do not allow or create an engine misfire in one or more cylinders for an extended period of time. Damage to converter from overheating may occur due to loading with unburned fuel.

TESTING

ENGINE COMPRESSION

Check compression pressure with engine at normal operating temperature, all spark plugs removed, throttle and choke valves wide open and engine at cranking speed.

COMPRESSION SPECIFICATIONS TABLE

Application Specification

Compression Ratio 9.2:1

Compression Pressure 120-150 psi (8.4-10.5 kg/cm)

Maximum Variation Between Cylinders . 30 psi (2.1 kg/cm)

HIGH TENSION WIRE RESISTANCE

Do not puncture spark plug wires with any type of probe. Remove spark plug wire and check resistance using an ohmmeter.

SPARK PLUGS

SPARK PLUG TYPE TABLE

Application Champion No.

All Models RFN14LY

SPARK PLUG SPECIFICATIONS TABLE

Gap: In. (mm) Torque: Ft. Lbs. (N.m)

0.035 (0.89) 7-15 (10-20)

FUEL PUMP

4.0L

  1. Remove the cap from the pressure test port located in the
    fuel rail. See Fig.     1. Connect Fuel Pressure Gauge (J-34730-1) to the
    pressure fitting.

  2. Start vehicle. Pressure should be approximately 31 psi (2.
    1 kg/cm) with the vacuum hose connected to the pressure regulator and
    39 psi (2.6 kg/cm) with the vacuum hose removed from the pressure
    regulator. See FUEL PUMP SPECIFICATIONS TABLE.

  3. Check the fuel pump flow rate. A good fuel pump will
    deliver at least one liter of fuel per minute with the fuel return
    line pinched off. If the fuel pump does not pump adequately, inspect
    the fuel system for a plugged fuel filter or filter sock.

  4. Fuel pump flow rate can be checked by connecting one end
    of an old A/C gauge hose to the fuel test port on the fuel rail and
    inserting the other end of the hose into a container of at least one
    liter or more capacity.

  5. Run the fuel pump by installing a jumper wire into

diagnostic connector terminals D1-5 and D1-6. Be sure to pinch off the fuel return line or most of the fuel will be returned to the fuel tank.

Fig. 1: Fuel System Pressure Test Components Courtesy of American Motors/Jeep Corp.

4.2L

Perform fuel pump test with air cleaner removed and fuel

inlet line or filter disconnected at carburetor. Disconnect fuel return line at fuel filter and plug nipple on filter. Make all tests at idle speed. See FUEL PUMP SPECIFICATIONS TABLE.

FUEL PUMP SPECIFICATIONS TABLE

Application Pressure Volume

** psi (kg/cm2)(1) Pts. (L)

4.0L (2) 31 (2.1) 1.0 (.47)

4.0L (3) 39 (2.6) 1.0 (.47) Hiroshi suzuki romance download.

4.2L 4.0-5.0 (.28-.35) 1.0 (.47)

  1. - Volume per 30 seconds.

  2. - With the vacuum hose connected to the pressure regulator.

  3. - With the vacuum hose removed from the pressure regulator.

ADJUSTMENTS

VALVE ARRANGEMENT

* E-I-I-E-I-E-E-I-E-I-I-E (Front-to-rear).

VALVE CLEARANCE

All engines are equipped with hydraulic lifters. Valve clearance is not adjustable.

IGNITION COIL WIRE

Remove ignition coil wire from coil and distributor cap. Check terminals for corrosion and clean (if necessary). Check coil wire resistance. Replace wire if resistance is excessive.

HIGH TENSION WIRE RESISTANCE (OHMS) TABLE

Wire Length Minimum Maximum

0-15' 3000 10,000

15-25' 4000 15,000

25-35' 6000 20,000

Over 35' 8000 25,000

DISTRIBUTOR

4.0L

Information not available from manufacturer.

4.2L

All models are equipped with Motorcraft Solid State Ignition (SSI) systems. No adjustments are required.

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.

  1. 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.

  2. 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
ApplicationMan. Trans.Auto. Trans.

50 State 9 @ 1600 9 @ 1600

High Altitude 16 @ 1600 16 @ 1600

HOT (SLOW) IDLE RPM

4.0L


98 Jeep Grand Cherokee

Fig. 3: Diagnostic Connector Terminal Identification Courtesy of Chrysler Motors.


  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. 4: Installing Air Stepper Motor Exerciser Courtesy of Chrysler Motors.

  1. 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.

  2. 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.

  3. 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.

Fig. 5: Adjusting Idle RPM Courtesy of Chrysler Motors.

6) Adjust idle RPM screw to obtain idle speed of 750F50 RPM. Once correct idle RPM is obtained, seal the welch plug cavity with RTV sealant. Reconnect air stepper motor and TPS.

4.2L

  1. Warm engine to normal operating temperature. Apply parking
    brake. Place automatic transmission in Drive (Neutral on manual
    transmission)    . Disconnect and plug vacuum hose from vacuum actuator.
    Disconnect solenoid wire connector.

  2. Adjust curb idle screw to obtain correct curb idle. See
    CURB IDLE SPEED (RPM) table. Apply 10-15 in. Hg vacuum to vacuum
    actuator. With throttle positioner fully extended, adjust screw on
    throttle lever, to set vacuum actuator RPM to specification. See
    VACUUM ACTUATOR & SOLENOID IDLE (RPM) table. Disconnect vacuum pump.

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  3. Apply battery voltage to solenoid with a jumper wire. Turn
    A/C on (if equipped). Open throttle, allowing solenoid to fully
    extend. Adjust solenoid adjusting screw to obtain solenoid idle RPM.

See VACUUM ACTUATOR & SOLENOID IDLE (RPM) table. Reconnect solenoid connector and vacuum hose.

CURB IDLE SPEED (RPM) TABLE - 4.2L

Application Man. Trans. Auto. Trans.

50 State 680 600

High Altitude 700 650

VACUUM ACTUATOR & SOLENOID IDLE (RPM) TABLE - 4.2L
ApplicationVacuum Actuator Solenoid Energized

Man. Trans 1100 900

Auto. Trans 900 800

Fig. 6: Adjusting 4.2L Idle RPM Courtesy of Chrysler Motors.

NOTE: Idle mixture adjustment is not part of a normal tune-up. DO NOT adjust mixture unless carburetor has been disassembled

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

Application Man. Trans. Auto. Trans.

4.2L 50 50

THROTTLE POSITION SENSOR (TPS)

Jeep Grand Cherokee Performance

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.

  1. 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.

  2. 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.

  3. Adjust sensor to obtain correct output voltage. Tighten
    retaining screws. Remove voltmeter.

COLD (FAST) IDLE RPM

4.2L

Jeep Cherokee Performance Parts

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

Application Man. Trans. Auto. Trans.

4.2L 1700 1700

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 @ 75F (24C)
Application Specification
All Models 400-800

TOTAL SPARK ADVANCE TABLE @ 2000 RPM


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. IGNITION COIL

IGNITION COIL OUTPUT TABLE @ 1000 RPM


Application Output

All Models 24KV Minimum

IGNITION COIL RESISTANCE TABLE


Temperature Primary Ohms Secondary Ohms

75F(24C) 1.13-1.23 7700-9300

200F(93C) 1.5 12,000

FUEL SYSTEM

CARBURETORS & FUEL INJECTION TABLE


Application Model

4.0L MPFI

4 . 2L Carter BBD 2-Bbl .

BATTERY

BATTERY SPECIFICATIONS TABLE


Application Cold Cranking Reserve Capacity

** (1) AmpsMinutes

Standard 421 75

Optional 452 81

(1) - At 0F (-18C).


STARTER

All models equipped with Mitsubishi starters. STARTER SPECIFICATIONS TABLE

Application Volts Amps Test RPM
All Models 11.22 80 2500

ALTERNATOR

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

ALTERNATOR SPECIFICATIONS TABLE

Application Field Current Rated

Application

**Draw @ 12 VoltsAmp Output

98 Jeep Cherokee For Sale

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Standard (1) 4.0-5.0 Amps 56

Optional (1) 4.0-5.0 Amps 66

Optional (1) 4.0-5.0 Amps 78

(1) - At 80F (27C).

ALTERNATOR REGULATORS

All models use Delco-Remy solid state regulators, integral with alternator. Regulator is nonadjustable.

BELT ADJUSTMENT

BELT ADJUSTMENT TABLE TENSION IN LBS. (KG) USING STRAND TENSION GAUGE
Application New Belts Used Belts

'V'-Belts 125-155 (57-70) 90-115 (41-52)

Serpentine 180-200 (82-91) 140-160 (63-72)

REPLACEMENT INTERVALS

REPLACEMENT INTERVALS TABLE

Component Interval (Miles)

Air Filter 30,000

Fuel Filter 30,000

Oil & Filter 7500

PCV Valve 30,000

Spark Plugs 30,000

CAPACITIES

FLUID CAPACITIES TABLE

Application Quantity

Auto. Trans. (Dexron II)

Wrangler 8.0 qts. (7.6L)

All Others 8.5 qts. (8.0L)

Cooling System

Wrangler 10.5 qts. (9.9L)

All Others 12.0 qts. (11.4L)

Crankcase (Includes Filter)

Wrangler 5.0 qts. (4.7L)

All Others 6.0 qts. (5.7L)

Drive Axle

Front 2.5 pts. (1.2L)

Rear

Comanche

Standard Capacity 2 . 5 pts . (1.2L)

Metric Ton Axle 4.8 pts. (2.3L)

All Others 2.5 pts. (1.2L)

Fuel Tank

Cherokee & Wagoneer

Standard 13.5 gals. (51L)

Jeep Cherokee Performance Upgrades

Optional 20 gals. (76L)

Comanche

Standard 16 gals. (60L)

Optional 23.5 gals. (89L)

Wrangler

Standard 15 gals. (57L)

Jeep Grand Cherokee Performance Upgrades

Optional 20 gals. (75L)

Manual Transmission

AX4 7.8 pts. (3.7L)

AX5 7.4 pts. (3.5L)

BA 10/5 3.5 pts. (1.6L)

98 Jeep Cherokee Parts

Transfer Case (Dexron II)

Wrangler 3.25 pts. (1.5L)

All Others

Command Trac 2 . 2 pts . (1. 0L)

Select Trac 3.0 pts. (1.4L)

SYSTEM REFRIGERANT CAPACITIES TABLE

Application Ozs.

All Models 36