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Land Rover Defender 90 1997 – 1996 98 ENGINE PERFORMANCE Trouble Shooting No Codes Defender 90 Discovery

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Land Rover Defender 90 1997 - 1996-98 ENGINE PERFORMANCE Trouble Shooting - No Codes - Defender 90 & Discovery


Land Rover Defender 90 1997 - INTRODUCTION

Before diagnosing symptoms or intermittent faults, follow proper work flow. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. If no Diagnostic Trouble Codes (DTCs) are present and a no start condition exists, proceed to appropriate BASIC DIAGNOSTIC PROCEDURES article. If no DTCs are present and a driveability condition exists, diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).

NOTE: Some 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.

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 TESTING article. For specifications, see ON-VEHICLE ADJUSTMENTS or SERVICE & ADJUSTMENT SPECIFICATIONS article.


Land Rover Defender 90 1997 - SYMPTOMS SYMPTOM DIAGNOSIS


CAUTION: When battery is disconnected, vehicle computer may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting the battery.

Symptom checks cannot be used properly unless problem occurs while vehicle is being tested. To reduce diagnostic time, ensure steps in appropriate BASIC DIAGNOSTIC PROCEDURES article and appropriate SELF-DIAGNOSTICS article were performed before diagnosing a symptom. Following symptoms are available for diagnosis:


Land Rover Defender 90 1997 - ENGINE DOES NOT START (DOES NOT TURN OVER)


  • Check for security system malfunction (if equipped).
  • Check battery and cables, charging system and fusible links.
  • Starter motor inoperative.
  • Check engine ground straps.
  • Faulty ignition switch.
  • Faulty Park/Neutral position switch.
  • Park/Neutral position switch misaligned or out of position.

Land Rover Defender 90 1997 - ENGINE HARD TO START (ENGINE TURNS OVER)


  • Check battery and cables, charging system and fusible links.
  • Low battery charge.
  • Check Crankshaft Position (CKP) sensor for correct installation.
  • Check clutch start switch (M/T) or Neutral start switch (A/T) for proper position and adjustment.
  • Check fuel level and ensure fuel is not contaminated.
  • Check Idle Air Control (IAC) valve.
  • Check main relay and fuel pump relay.
  • Check ignition switch sense signal.
  • Check ignition switch.
  • Check inertia fuel shut-off switch and ensure switch is closed.
  • Check starter relay.
  • Check starter and wiring connections.

Land Rover Defender 90 1997 - ENGINE HESITATES OR MISSES


  • Check for vacuum leaks.
  • Check air filter.
  • Verify secondary ignition system performance.
  • Verify proper compression and valve clearance.
  • Check ignition coils.
  • Check operation of injectors.
  • Check vehicle speed sensor.

Land Rover Defender 90 1997 - ENGINE KNOCK


  • Blown head gasket.
  • Incorrect valve timing.
  • Lean fuel mixture.
  • Low coolant in radiator/engine (engine overheating).
  • Check installation of knock sensors.
  • Stuck thermostat (engine overheating).
  • Wrong octane fuel.

Land Rover Defender 90 1997 - LOSS OF POWER


  • Burnt or sticking valves.
  • Ensure engine compression is okay.
  • Fuel system malfunction.
  • Incorrect camshaft timing.
  • Incorrect valve clearance.
  • Ignition system malfunction.
  • Wrong octane fuel.

Land Rover Defender 90 1997 - POOR FUEL MILEAGE


  • Check for vacuum leaks.
  • Check air filter.
  • Check idle speed and ensure base timing is correct.
  • Verify secondary ignition system performance.
  • Verify proper compression and valve clearance.

Land Rover Defender 90 1997 - ROUGH OR UNSTABLE IDLE


  • Check for vacuum leaks.
  • Check air filter.
  • Check Idle Air Control (IAC) valve.
  • Check idle speed and ensure base timing is correct.
  • Verify secondary ignition system performance.
  • Verify proper compression and valve clearance.

Land Rover Defender 90 1997 - INTERMITTENTS 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 Land Rover TestBook, an OBD-II scan tool or a DVOM while attempting to reproduce conditions causing intermittent fault. A status change indicates a fault has been located.

Use a Land Rover TestBook, an OBD-II scan tool or 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 during test procedures indicate area of fault.


Land Rover Defender 90 1997 - TEST PROCEDURES Intermittent Simulation


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

  • Lightly vibrate component.
  • Heat component to normal operating temperature.
  • Wiggle or bend wiring harness.
  • Spray component with a water mist.
  • 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.