Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSJAGUAR1991XJ-6 L6-4.0LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTEMISSION CONTROL SYSTEMSTESTING AND INSPECTIONDIAGNOSTIC NOTES
1991 Jaguar XJ-6 L6-4.0L
Diagnostic Notes
1991 Jaguar XJ-6 L6-4.0LSECTION Diagnostic Notes
This section is used to find the correct test procedure for a given symptom. Symptoms and actions in this section are for EMISSION CONTROL DEVICES. Refer to FUEL SYSTEM SUPPLY AND AIR INDUCTION SYSTEMS and COMPUTERS AND CONTROL SYSTEMS for diagnosis related to those systems. Verify correct system application to ensure that vehicle has given component(s).
Before proceding to appropriate symptom, perform the following visual inspections:
1. Vacuum hoses for splits, kinks and proper routing.
2. Ignition wires for cracking, hardness and proper connections at both distributor and spark plugs.
3. All wiring for proper connections, pinches, routing, and cuts.
NOTE: Catalytic converters and feedback systems do not operate until they are at normal operating temperature. It is essential that the vehicle has been properly warmed up and is at operating temperature (except when attempting to diagnosis a cold driveability problem). Failure to do so will result in inaccurate test results.
Before proceding to appropriate symptom, perform the following visual inspections:
1. Vacuum hoses for splits, kinks and proper routing.
2. Ignition wires for cracking, hardness and proper connections at both distributor and spark plugs.
3. All wiring for proper connections, pinches, routing, and cuts.
NOTE: Catalytic converters and feedback systems do not operate until they are at normal operating temperature. It is essential that the vehicle has been properly warmed up and is at operating temperature (except when attempting to diagnosis a cold driveability problem). Failure to do so will result in inaccurate test results.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.