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Jaguar XJ6 1995 – 1995 ENGINE PERFORMANCE Trouble Shooting No Codes 4 0L 6 Cyl

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Jaguar XJ6 1995 - 1995 ENGINE PERFORMANCE Trouble Shooting - No Codes - 4.0L 6-Cyl.


Jaguar XJ6 1995 - INTRODUCTION

Before diagnosing symptoms or intermittent faults, perform steps in BASIC TESTING article and TESTS W/CODES article. Use this article to diagnose driveability problems existing when a hard fault code is not present.

NOTE: Some driveability problems may have been corrected by manufacturer with a revised Powertrain Control Module (PCM). Check with manufacturer for latest PCM 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 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. See INTERMITTENT PROBLEM DIAGNOSIS under INTERMITTENTS.

NOTE: For specific testing procedures, see SYSTEM/COMPONENT TESTS article. For specifications, see ADJUSTMENTS - 4.0L 6-CYL article or SPECIFICATIONS - 4.0L 6-CYL article.


Jaguar XJ6 1995 - SYMPTOMS SYMPTOM DIAGNOSIS


Symptom checks cannot be used properly unless the problem occurs while the vehicle is being tested. To reduce diagnostic time, ensure steps in BASIC TESTING article and TESTS W/CODES articles were performed before diagnosing a symptom.

Symptoms available for diagnosis include:

  • Detonation (Engine Knock)
  • Difficult Start (Cranks Okay)
  • Engine Backfires
  • Engine Does Not Start (Fails To Rotate)
  • Engine Fails To Idle
  • Engine Rotates, But Fails To Start
  • Engine Runs Rough (Off Idle)
  • Engine Stalls
  • Loss Of Power
  • Rough Or Unstable Idle

Jaguar XJ6 1995 - DETONATION (ENGINE KNOCK)


  • Blown head gasket.
  • Ignition timing too far advanced.
  • Incorrect valve timing.
  • Lean fuel mixture.
  • No coolant in radiator/engine (engine overheating).
  • Stuck thermostat (engine overheating).
  • Wrong octane fuel.

Jaguar XJ6 1995 - DIFFICULT START (CRANKS OKAY)


  • Check air induction system for cracks and restriction.
  • Check airflow sensor plate rest position.
  • Check engine coolant temperature sensor operation.
  • Check for cracks and poor connections at throttle body.
  • Check ignition coil primary connections and wiring harness.
  • Ensure EGR valve operation is correct.
  • Ensure electrical harness and connectors are not broken or loose.
  • Ensure engine has sufficient compression.
  • Ensure fuel injector operation is correct.
  • Ensure fuel system pressure and volume are correct.
  • Ensure fuel system residual pressure is correct.
  • Ensure ignition and valve timing are correct.
  • Ensure ignition coil resistance is within specification.
  • Ensure PCM has correct voltage supply and is properly grounded.
  • Ensure vacuum hoses are not disconnected or damaged.

Jaguar XJ6 1995 - ENGINE BACKFIRES


  • Air leak into/from exhaust system.
  • Air leak past valve guides or valves.
  • Incorrect ignition timing.
  • Incorrect valve timing.
  • Intake manifold air leak.
  • Lean air/fuel mixture.
  • Valves sticking open.

Jaguar XJ6 1995 - ENGINE DOES NOT START (FAILS TO ROTATE)


  • Battery not fully charged.
  • Loose or corroded battery terminals.
  • Starter motor inoperative.

Jaguar XJ6 1995 - ENGINE FAILS TO IDLE


  • Blocked or restricted exhaust system.
  • Blown head gasket.
  • Incorrect ignition timing.
  • Incorrect valve clearance.

Jaguar XJ6 1995 - ENGINE ROTATES, BUT FAILS TO START


  • Fuel system malfunction.
  • Ignition system malfunction.
  • Starter motor rotating too slowly.

Jaguar XJ6 1995 - ENGINE RUNS ROUGH (OFF IDLE)


  • Blown head gasket.
  • Blown exhaust system.
  • Broken valve spring(s).
  • Burnt valve or valve seat.
  • Fuel system malfunction.
  • Ignition system malfunction.
  • Intake manifold air leak.
  • Sticking valves.

Jaguar XJ6 1995 - ENGINE STALLS


  • Check EGR system for correct operation.
  • Check engine coolant temperature sensor operation.
  • Check for cracks and poor connections at throttle body.
  • Check for distortion and cracks in fuel injector plastic connecting flanges.
  • Check for poor quality fuel, fuel with high alcohol content or contaminated fuel.
  • Check throttle position sensor operation.
  • Ensure air intake system is unrestricted.
  • Ensure fuel system pressure is correct.
  • Ensure PCV system operation is correct.

Jaguar XJ6 1995 - 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.

Jaguar XJ6 1995 - ROUGH OR UNSTABLE IDLE


  • Burnt valve or valve seat.
  • Fuel system malfunction.
  • Incorrect valve clearance.
  • Incorrect valve timing.
  • Incorrect ignition timing.
  • Ignition system malfunction.
  • Sticking valves.

Jaguar XJ6 1995 - 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 Diagnostic Trouble Code (DTC) which may help in diagnosis.

If problem vehicle does not produce a DTC, monitor voltage or resistance values using a Digital Volt-Ohmmeter (DVOM) while attempting to reproduce conditions causing intermittent fault. A status change on DVOM indicates 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 indicate area of fault.


Jaguar XJ6 1995 - TEST PROCEDURES Intermittent Simulation


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

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

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