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Jeep Grand Wagoneer 1991 – H TESTS W O CODES 1991 ENGINE PERFORMANCE Trouble Shooting No Codes

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Jeep Grand Wagoneer 1991 - H - TESTS W/O CODES 1991 ENGINE PERFORMANCE Trouble Shooting No Codes


Jeep Grand Wagoneer 1991 - INTRODUCTION

Before diagnosing symptoms or intermittent faults, perform BASIC DIAGNOSTIC PROCEDURES in the BASIC TESTING and DIAGNOSTIC TESTS in the TESTS W/CODES articles in this section. Use this article to diagnose driveability problems existing when a hard fault code is not present or vehicle is not equipped with a self-diagnostic system.

NOTE: Some manufacturer driveability problems may have been corrected by manufacturer with a revised computer calibration chip or computer control unit. Check with manufacturer for latest chip or computer application.

Symptom checks can direct the technician to malfunctioning component(s) for further diagnosis. A symptom should lead to a specific component, system test or an adjustment.

Use intermittent test procedures to locate driveability problems that do not occur when the vehicle is being tested. These test procedures should also be used if a soft (intermittent) trouble code was present, but no problem was found during self-diagnostic testing.

NOTE: For specific testing procedures, see appropriate SYSTEM/COMPONENT TESTS : - the following list.

For specifications, refer to the appropriate ADJUSTMENTS or SPECIFICATIONS article.


Jeep Grand Wagoneer 1991 - SYMPTOMS SYMPTOM DIAGNOSIS


Symptom checks cannot be used properly unless problem occurs while vehicle is being tested. To reduce diagnostic time, ensure BASIC DIAGNOSTIC PROCEDURES in the BASIC TESTING and DIAGNOSTIC TESTS in the TESTS W/CODES articles in the ENGINE PERFORMANCE Section were performed before diagnosing a symptom. Following are some symptoms available for diagnosis.

  • Erratic Timing Advance
  • Timing Not Affected By Vacuum
  • Engine Does Not Operate Smoothly Or Misfires At High Speed
  • Engine Fails To Start
  • Engine Backfires, Fails To Start
  • Engine Continues To Run With Key Off
  • Engine Runs Only With Key In Start Position
  • Excessive Fuel Consumption
  • Intermittent Spark

Jeep Grand Wagoneer 1991 - ERRATIC TIMING ADVANCE


Check vacuum advance mechanism and centrifugal advance weights (5.9L engine). See appropriate SYSTEM/COMPONENT TESTS article in this section. See list below.


Jeep Grand Wagoneer 1991 - TIMING NOT AFFECTED BY VACUUM


Check vacuum advance mechanism and adjusting screws (5.9L engine). See appropriate SYSTEM/COMPONENT TESTS article in this section. See list below.

Check pickup coil pivot for corrosion (5.9L engine only). See BASIC TESTING article.


Jeep Grand Wagoneer 1991 - ENGINE DOES NOT OPERATE SMOOTHLY OR MISFIRES AT HIGH SPEED


Check spark plugs, spark advance, ignition system wires and connections. Check starter solenoid for shorting at terminal "S" (5.9L engine). Check for missing trigger wheel pin (5.9L engine). See BASIC TESTING article in this section.


Jeep Grand Wagoneer 1991 - ENGINE FAILS TO START - NO SPARK AT PLUGS


Check for open, loose or corroded ground wires in distributor, and check primary wiring circuits. See BASIC TESTING article in this section. Check for defective ignition module, cracked distributor cap and defective rotor. See the BASIC TESTING article in this section.


Jeep Grand Wagoneer 1991 - ENGINE BACKFIRES, FAILS TO START


Verify ignition timing is correct, check for moisture in distributor or faulty distributor cap and verify that ignition wires are connected in proper firing order. See BASIC TESTING article in this section.


Jeep Grand Wagoneer 1991 - ENGINE CONTINUES TO RUN WITH KEY OFF


Check for defective starter motor solenoid. See the appropriate SYSTEM/COMPONENT TESTS article. See list below.

Check for shorted diode in alternator warning light circuit. See appropriate SYSTEM/COMPONENT TESTS article. See list above.


Jeep Grand Wagoneer 1991 - ENGINE RUNS ONLY WITH KEY IN START POSITION


Check resistance wire for open circuit or excessive resistance (5.9L engine). See appropriate SYSTEM/COMPONENT TESTS article. See list below.


Jeep Grand Wagoneer 1991 - EXCESSIVE FUEL CONSUMPTION


Check for incorrect ignition timing. Check vacuum advance mechanism and centrifugal advance weights (5.9L engine). See appropriate SYSTEM/COMPONENT TESTS article. See list below.


Jeep Grand Wagoneer 1991 - INTERMITTENT SPARK


Check for loose or corroded terminals. Check for loose ground connector or shorted wires in distributor (5.9L engine). Check for missing trigger wheel pin or for defective pick-up coil or ignition module (5.9L engine).


Jeep Grand Wagoneer 1991 - INTERMITTENTS INTERMITTENT PROBLEM DIAGNOSIS


Intermittent fault testing requires duplicating circuit or component failure to identify the problem. These procedures may lead to the computer setting a fault code (on some systems) which may help in diagnosis.

If problem vehicle does not produce fault codes, monitor voltage or resistance values using a DVOM, while attempting to reproduce conditions causing intermittent fault. A change in status on DVOM will indicate a fault has been located.

Use a DVOM to pinpoint faults. When monitoring voltage, ensure ignition switch is in ON position or engine is running. Ensure ignition switch is in OFF position or negative battery cable is disconnected when monitoring circuit resistance. Status changes on DVOM during test procedures will indicate area of fault.


Jeep Grand Wagoneer 1991 - TEST PROCEDURES Intermittent Simulation


To reproduce conditions creating an intermittent fault, use following methods:

  • Lightly vibrate component.
  • Heat component.
  • Wiggle or bend wiring harness.
  • Spray component with water.
  • Remove/apply vacuum source.

Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for self-diagnostic codes. Use test results to identify a faulty component or circuit.